That is, "There are three in heaven which do bear record to this truth here upon earth, namely, that Jesus is the Christ; that is to say, the three persons in the Holy Trinity, The Father, the Word, and the Holy Ghost; the Father bore witness both at Christ's baptism and transfiguration also, when with an audible voice he declared, This is my beloved Son, in whom I am well pleased.
The Word bore record of himself, affirming frequently, plainly, and directly, that he was the Son of God, and making it manifest, by his doctrine and miracles, that he came from the Father; the Spirit bore witness to this, partly by descending on Christ at his baptism in the shape of a dove, and partly by descending on his apostles in the feast of Pentecost in the figure of fiery tongues, Act_2:1"
Learn hence, 1. That it was no easy matter to believe the truth of our Saviour's mission and miracles, and that Jesus Christ was the essential and natural Son of God. Though by the mouth of two or three witnesses every truth is established, yet in this and the next verse we have no less than six witnesses produced to prove our Jesus to be the Son of God, three heavenly, and three earthly witnesses. -- It is added, these three are one, one in testimony, say the adversaries of the Trinity, but not one in essence. One in both, say we, as one in testimony, so one in essence.
But suppose that we should grant that the oneness spoken of in the text is to be expounded of consent in testimony, agreement, and will, principally, yet will it prove the Godhead of Christ, and of the Holy Ghost; for in free agents, where there is the same will, there is the same nature: With men it is the same specifical nature; but with God, because there in but one only God, therefore it must be the same numerical nature.
Learn, 2. That there are three persons, yet but one God, that do bear witness to the divinity of Christ, and of the plenteous redemption wrought by him.