John the Apostle
John 15:27ESV·traditional attribution

And you also will bear witness, because you have been with me from the beginning.

John Calvin Reformed @genevareformer

27. And you also bear testimony. Christ means that the testimony of the Spirit will not be of such a nature that the apostles shall have it for their private advantage, or that they alone shall enjoy it, but that by them it will be widely diffused, because they will be organs of the Holy Spirit, as indeed, he spoke by their mouth.

Matthew Henry Presbyterian @wholebiblehenry

Christ having spoken of the great opposition which his gospel was likely to meet with in the world, and the hardships that would be put upon the preachers of it, lest any should fear that they and it would be run down by that violent torrent, he here intimates to all those that were well-wishers to his cause and interest what effectual provision was made...

Commenting on John 15:26-27

Albert Barnes Presbyterian @notesbybarnes

Verse 27. Ye also shall bear witness. You shall be witnesses to the world to urge on them the evidences that the Lord Jesus is the Messiah. Have been with me. They had for more than three years seen his works, and were therefore qualified to bear witness of his character and doctrines. From the beginning. From his entrance on the public work of the ministry, . Comp. .