John the Apostle
1 John 4:14ESV·traditional attribution

And we have seen and testify that the Father has sent his Son to be the Savior of the world.

John Calvin Reformed @genevareformer

14 And we have seen He now explains the other part of the knowledge of God, which we have referred to, that he communicates himself to us in his Son, and offers himself to be enjoyed in him. It hence follows, that he is by faith received by us.

Matthew Henry Presbyterian @wholebiblehenry

Since faith in Christ works love to God, and love to God must kindle love to the brethren, the apostle here confirms the prime article of the Christian faith as the foundation of such love. Here, I. He proclaims the fundamental article of the Christian religion, which is so representative of the love of God: And we have seen, and do testify, that the Father...

Commenting on 1 John 4:14-16

John Gill Reformed Baptist @doctorgill

And we have seen, and do testify,.... This seems to be particularly said of the apostles, who had a clear discerning of the love and grace of God, manifested in the mission of Christ into the world; for though no man had seen his nature and his person, yet they had seen his love, and the exceeding riches of his grace, which he had shown...