Thomas Aquinas on the Symbolism of the Ark of the Covenant

 Thomas Aquinas (link to source), Summa Theologica, Second Part of the Second Part, Treatise on the Theological Virtues, Question 33, Article 4: 

Whether a man is bound to correct his prelate?

Objection 1: It would seem that no man is bound to correct his prelate. For it is written (Ex. 19:12): "The beast that shall touch the mount shall be stoned," [*Vulg.: 'Everyone that shall touch the mount, dying he shall die.'] and (2 Kings 6:7) it is related that the Lord struck Oza for touching the ark. Now the mount and the ark signify our prelates. Therefore prelates should not be corrected by their subjects.

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Reply to Objection 1: It would seem that a subject touches his prelate inordinately when he upbraids him with insolence, as also when he speaks ill of him: and this is signified by God's condemnation of those who touched the mount and the ark.

For those who are interested in such things, no orthodox Roman Catholic theologian would refer to Mary as a prelate.

Thomas Aquinas (link to source), Summa Theologica, First Part of the Second Part, Treatise on Law, Question 102, Article 4: 

Whether sufficient reason can be assigned for the ceremonies pertaining to holy things?

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Objection 6: Further, the Lord commanded (Ex. 20:4) that they should "not make . . . a graven thing, nor the likeness of anything." It was therefore unfitting for graven images of the cherubim to be set up in the tabernacle or temple. In like manner, the ark, the propitiatory, the candlestick, the table, the two altars, seem to have been placed there without reasonable cause.

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Reply to Objection 6: Both literal and figurative reasons may be assigned for the things contained in the tabernacle. The literal reason is in connection with the divine worship. And because, as already observed (ad 4), the inner tabernacle, called the Holy of Holies, signified the higher world of spiritual substances, hence that tabernacle contained three things, viz. "the ark of the testament in which was a golden pot that had manna, and the rod of Aaron that had blossomed, and the tables" (Heb. 9:4) on which were written the ten commandments of the Law. Now the ark stood between two "cherubim" that looked one towards the other: and over the ark was a table, called the "propitiatory," raised above the wings of the cherubim, as though it were held up by them; and appearing, to the imagination, to be the very seat of God. For this reason it was called the "propitiatory," as though the people received propitiation thence at the prayers of the high-priest. And so it was held up, so to speak, by the cherubim, in obedience, as it were, to God: while the ark of the testament was like the foot-stool to Him that sat on the propitiatory. These three things denote three things in that higher world: namely, God Who is above all, and incomprehensible to any creature. Hence no likeness of Him was set up; to denote His invisibility. But there was something to represent his seat; since, to wit, the creature, which is beneath God, as the seat under the sitter, is comprehensible. Again in that higher world there are spiritual substances called angels. These are signified by the two cherubim, looking one towards the other, to show that they are at peace with one another, according to Job 25:2: "Who maketh peace in . . . high places." For this reason, too, there was more than one cherub, to betoken the multitude of heavenly spirits, and to prevent their receiving worship from those who had been commanded to worship but one God. Moreover there are, enclosed as it were in that spiritual world, the intelligible types of whatsoever takes place in this world, just as in every cause are enclosed the types of its effects, and in the craftsman the types of the works of his craft. This was betokened by the ark, which represented, by means of the three things it contained, the three things of greatest import in human affairs. These are wisdom, signified by the tables of the testament; the power of governing, betokened by the rod of Aaron; and life, betokened by the manna which was the means of sustenance. Or else these three things signified the three Divine attributes, viz. wisdom, in the tables; power, in the rod; goodness, in the manna---both by reason of its sweetness, and because it was through the goodness of God that it was granted to man, wherefore it was preserved as a memorial of the Divine mercy. Again, these three things were represented in Isaias' vision. For he "saw the Lord sitting upon a throne high and elevated"; and the seraphim standing by; and that the house was filled with the glory of the Lord; wherefrom the seraphim cried out: "All the earth is full of His glory" (Is. 6:1, 3). And so the images of the seraphim were set up, not to be worshipped, for this was forbidden by the first commandment; but as a sign of their function, as stated above.

The outer tabernacle, which denotes this present world, also contained three things, viz. the "altar of incense," which was directly opposite the ark; the "table of proposition," with the twelve loaves of proposition on it, which stood on the northern side; and the "candlestick," which was placed towards the south. These three things seem to correspond to the three which were enclosed in the ark; and they represented the same things as the latter, but more clearly: because, in order that wise men, denoted by the priests entering the temple, might grasp the meaning of these types, it was necessary to express them more manifestly than they are in the Divine or angelic mind. Accordingly the candlestick betokened, as a sensible sign thereof, the wisdom which was expressed on the tables (of the Law) in intelligible words. The altar of incense signified the office of the priest, whose duty it was to bring the people to God: and this was signified also by the rod: because on that altar the sweet-smelling incense was burnt, signifying the holiness of the people acceptable to God: for it is written (Apoc. 8:3) that the smoke of the sweet-smelling spices signifies the "justifications of the saints" (cf. Apoc. 19:8). Moreover it was fitting that the dignity of the priesthood should be denoted, in the ark, by the rod, and, in the outer tabernacle, by the altar of incense: because the priest is the mediator between God and the people, governing the people by Divine power, denoted by the rod; and offering to God the fruit of His government, i.e. the holiness of the people, on the altar of incense, so to speak. The table signified the sustenance of life, just as the manna did: but the former, a more general and a coarser kind of nourishment; the latter, a sweeter and more delicate. Again, the candlestick was fittingly placed on the southern side, while the table was placed to the north: because the south is the right-hand side of the world, while the north is the left-hand side, as stated in De Coelo et Mundo ii; and wisdom, like other spiritual goods, belongs to the right hand, while temporal nourishment belongs on the left, according to Prov. 3:16: "In her left hand (are) riches and glory." And the priestly power is midway between temporal goods and spiritual wisdom; because thereby both spiritual wisdom and temporal goods are dispensed.

Another literal signification may be assigned. For the ark contained the tables of the Law, in order to prevent forgetfulness of the Law, wherefore it is written (Ex. 24:12): "I will give thee two tables of stone, and the Law, and the commandments which I have written: that thou mayest teach them" to the children of Israel. The rod of Aaron was placed there to restrain the people from insubordination to the priesthood of Aaron; wherefore it is written (Num. 17:10): "Carry back the rod of Aaron into the tabernacle of the testimony, that it may be kept there for a token of the rebellious children of Israel." The manna was kept in the ark to remind them of the benefit conferred by God on the children of Israel in the desert; wherefore it is written (Ex. 16:32): "Fill a gomor of it, and let it be kept unto generations to come hereafter, that they may know the bread wherewith I fed you in the wilderness." The candlestick was set up to enhance the beauty of the temple, for the magnificence of a house depends on its being well lighted. Now the candlestick had seven branches, as Josephus observes (Antiquit. iii, 7,8), to signify the seven planets, wherewith the whole world is illuminated. Hence the candlestick was placed towards the south; because for us the course of the planets is from that quarter. The altar of incense was instituted that there might always be in the tabernacle a sweet-smelling smoke; both through respect for the tabernacle, and as a remedy for the stenches arising from the shedding of blood and the slaying of animals. For men despise evil-smelling things as being vile, whereas sweet-smelling things are much appreciated. The table was place there to signify that the priests who served the temple should take their food in the temple: wherefore, as stated in Mat. 12:4, it was lawful for none but the priests to eat the twelve loaves which were put on the table in memory of the twelve tribes. And the table was not placed in the middle directly in front of the propitiatory, in order to exclude an idolatrous rite: for the Gentiles, on the feasts of the moon, set up a table in front of the idol of the moon, wherefore it is written (Jer. 7:18): "The women knead the dough, to make cakes to the queen of heaven."

In the court outside the tabernacle was the altar of holocausts, on which sacrifices of those things which the people possessed were offered to God: and consequently the people who offered these sacrifices to God by the hands of the priest could be present in the court. But the priests alone, whose function it was to offer the people to God, could approach the inner altar, whereon the very devotion and holiness of the people was offered to God. And this altar was put up outside the tabernacle and in the court, to the exclusion of idolatrous worship: for the Gentiles placed altars inside the temples to offer up sacrifices thereon to idols.

The figurative reason for all these things may be taken from the relation of the tabernacle to Christ, who was foreshadowed therein. Now it must be observed that to show the imperfection of the figures of the Law, various figures were instituted in the temple to betoken Christ. For He was foreshadowed by the "propitiatory," since He is "a propitiation for our sins" (1 Jn. 2:2). This propitiatory was fittingly carried by cherubim, since of Him it is written (Heb. 1:6): "Let all the angels of God adore Him." He is also signified by the ark: because just as the ark was made of setim-wood, so was Christ's body composed of most pure members. More over it was gilded: for Christ was full of wisdom and charity, which are betokened by gold. And in the ark was a golden pot, i.e. His holy soul, having manna, i.e. "all the fulness of the Godhead" (Col. 2:9). Also there was a rod in the ark, i.e. His priestly power: for "He was made a . . . priest for ever" (Heb. 6:20). And therein were the tables of the Testament, to denote that Christ Himself is a lawgiver. Again, Christ was signified by the candlestick, for He said Himself (Jn. 8:12): "I am the Light of the world"; while the seven lamps denoted the seven gifts of the Holy Ghost. He is also betokened in the table, because He is our spiritual food, according to Jn. 6:41, 51: "I am the living bread": and the twelve loaves signified the twelve apostles, or their teaching. Or again, the candlestick and table may signify the Church's teaching, and faith, which also enlightens and refreshes. Again, Christ is signified by the two altars of holocausts and incense. Because all works of virtue must be offered to us to God through Him; both those whereby we afflict the body, which are offered, as it were, on the altar of holocausts; and those which, with greater perfection of mind, are offered to God in Christ, by the spiritual desires of the perfect, on the altar of incense, as it were, according to Heb. 13:15: "By Him therefore let us offer the sacrifice of praise always to God."

Emphasis is added by me.

Thomas Aquinas, Catena Aurea, at Matthew 27:35-38 (link to source):

Aug., in Serm., non occ.: Let your holiness consider of what might is the power of the cross. Adam set at nought the commandment, taking the apple from the tree; but all that Adam lost, Christ found upon the cross. The ark of wood saved the human race from the deluge of waters; when God’s people came out of Egypt, Moses divided the sea with his rod, overwhelmed Pharaoh, and redeemed God’s people. The same Moses changed the bitter water into sweet by casting wood into it. By the rod the refreshing stream was drawn out of the rock; that Amalech might be overcome, Moses’ outstretched hands were supported upon his rod; the Law of God is entrusted to the wooden ark of the covenant, that thus, by these steps we may come at last to the wood of the cross.

Thomas Aquinas, Summa Theologica, Third Part, Treatise on the Incarnation, Question 46, Article 4 (link to source)

Whether Christ ought to have suffered on the cross?

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I answer that, It was most fitting that Christ should suffer the death of the cross.

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The seventh reason is because this kind of death responds to very many figures. For, as Augustine says in a sermon on the Passion (Serm. ci De Tempore), an ark of wood preserved the human race from the waters of the Deluge; at the exodus of God's people from Egypt, Moses with a rod divided the sea, overthrew Pharaoh and saved the people of God. the same Moses dipped his rod into the water, changing it from bitter to sweet; at the touch of a wooden rod a salutary spring gushed forth from a spiritual rock; likewise, in order to overcome Amalec, Moses stretched forth his arms with rod in hand; lastly, God's law is entrusted to the wooden Ark of the Covenant; all of which are like steps by which we mount to the wood of the cross.