John Chrysostom

Then he answers, Lord, what wilt Thou have me to do? that none may say that he played the hypocrite, he that was even eager for blood, and went to the priests, and flung himself upon such dangers, in persecuting and bringing to punishment even them that were in foreign parts-under these circumstances he now acknowledges His sovereignty.

Homily on Acts 19 ↗

Ambrose of Milan

Although Paul was struck and taken up and was terrified because blindness had befallen him, still he began to come near when he said, "Lord, what will you have me do?" For that reason he is called the youngest by Christ, so that he who was called to grace could be excused from the guilt of his hazardous years. Yes, Christ saw him when the light shone round him; because young people are recalled from sin more by fear than by reason, Christ applied the goad and mercifully admonished him not to kick against it.

On Joseph the Patriarch ↗

Bede

Rise and enter the city, and you will be told what you must do. He did not immediately show him what was to be done but advised that it would be heard later in the city, so that he would stand more firmly in good things as he had previously fallen completely from his former error.

Commentary on Acts ↗