John the Apostle
1 John 1:3ESV·traditional attribution

that which we have seen and heard we proclaim also to you, so that you too may have fellowship with us; and indeed our fellowship is with the Father and with his Son Jesus Christ.

John Calvin Reformed @genevareformer

3 That which we have seen. He now repeats the third time the words, seen and heard, that nothing might be wanting as to the real certainty of his doctrine. And it ought to be carefully noticed, that the heralds of the Gospel chosen by Christ were those who were fit and faithful witnesses of all those things which they were to declare.

Matthew Henry Presbyterian @wholebiblehenry

The apostle omits his name and character (as also the author to the Hebrews does) either out of humility, or as being willing that the Christian reader should be swayed by the light and weight of the things written rather than by the name that might recommend them. And so he begins, I. With an account or character of the Mediator's person.

Commenting on 1 John 1:1-4

John Gill Reformed Baptist @doctorgill

That which we have seen and heard,.... This is repeated, both to confirm and illustrate what had been before said, and to carry on the discourse to what follows: declare we unto you; in the ministry of the word; the person and offices of Christ being the sum and substance of the Gospel ministration, that declares him to be the true God and eternal life...