On the theme of the Johannine Comma, the following is Wesley's brief take on the subject. I have presented Wesley mostly to show that I have not quoted Calvin above to support the argument by the personal authority of Calvin, but have simply included Calvin's comments (and Wesley's and others) to show the historical acceptance of the Comma.
The Authenticity of the Comma Johanneum
by John Wesley
excerpted from his
John Wesley's Explanatory Notes
7. What Bengelius has advanced, both concerning the transposition of these two verses, and the authority of the controverted verse, partly in his "Gnomon," and partly in his "Apparatus Criticus," will abundantly satisfy any impartial person. For there are three that testify - Literally, testifying, or bearing witness. The participle is put for the noun witnesses, to intimate that the act of testifying, and the effect of it, are continually present. Properly, persons only can testify; and that three are described testifying on earth, as if they were persons, is elegantly subservient to the three persons testifying in heaven. The Spirit - In the word, confirmed by miracles. The water - Of baptism, wherein we are dedicated to the Son, (with the Father and Spirit,) typifying his spotless purity, and the inward purifying of our nature. And the blood - Represented in the Lord's supper, and applied to the consciences of believer. And these three harmoniously agree in one - In bearing the same testimony, - that Jesus Christ is the divine, the complete, the only saviour of the world.