For thou shalt be his witness ... - As an apostle - to testify to all people that the Messiah has come, that he has died, that he has risen, and that he is the Saviour of the world.

Of what thou hast seen and heard - Of the remarkable proof which has been furnished you of the divine mission and character of the Lord Jesus.

Thou shalt be his witness unto all - Thou shalt proclaim Christ crucified, both to Jews and Gentiles.

For thou shalt be his witness unto all men,.... Gentiles as well as Jews, an eye and an ear witness to them;

of what thou hast seen and heard; as that he saw him personally and alive, and so could witness to the truth of his resurrection; for after he had been seen by all the apostles, he was last of all seen of Paul; and also, that he heard him and received from him the Gospel, and a mission and commission to preach it; for what he preached he did not receive of man, nor was he taught it by any, but he had it by revelation from Jesus Christ.

All men

He keeps back the offensive word Gentiles (Acts 9:15).

For thou shalt be his witness unto all men of what thou hast seen and heard.

22:12-21 The apostle goes on to relate how he was confirmed in the change he had made. The Lord having chosen the sinner, that he should know his will, he is humbled, enlightened, and brought to the knowledge of Christ and his blessed gospel. Christ is here called that Just One; for he is Jesus Christ the righteous. Those whom God has chosen to know his will, must look to Jesus, for by him God has made known his good-will to us. The great gospel privilege, sealed to us by baptism, is the pardon of sins. Be baptized, and wash away thy sins; that is, receive the comfort of the pardon of thy sins in and through Jesus Christ, and lay hold on his righteousness for that purpose; and receive power against sin, for the mortifying of thy corruptions. Be baptized, and rest not in the sign, but make sure of the thing signified, the putting away of the filth of sin. The great gospel duty, to which by our baptism we are bound, is, to seek for the pardon of our sins in Christ's name, and in dependence on him and his righteousness. God appoints his labourers their day and their place, and it is fit they should follow his appointment, though it may cross their own will. Providence contrives better for us than we do for ourselves; we must refer ourselves to God's guidance. If Christ send any one, his Spirit shall go along with him, and give him to see the fruit of his labours. But nothing can reconcile man's heart to the gospel, except the special grace of God.