3:21,22 Christ did not confess sin, as others did, for he had none to confess; but he prayed, as others did, and kept up communion with his Father. Observe, all the three voices from heaven, by which the Father bare witness to the Son, were pronounced while he was praying, or soon after, Lu 9:35; Joh 12:28. The Holy Ghost descended in a bodily shape like a dove upon him, and there came a voice from heaven, from God the Father, from the excellent glory. Thus was a proof of the Holy Trinity, of the Three Persons in the Godhead, given at the baptism of Christ.
Lu 3:21, 22. Baptism of and Descent of the Spirit upon Jesus.
(See on Mt 3:13-17.)
21. when all the people were baptized—that He might not seem to be merely one of the crowd. Thus, as He rode into Jerusalem upon an ass, "whereon yet never man sat" (Lu 19:30), and lay in a sepulchre "wherein was never man yet laid" (Joh 19:41), so in His baptism He would be "separate from sinners."