Acts 9:16

How great things he must suffer - Instead of proceeding as a persecutor, and inflicting sufferings on others, I will show him how many things he himself must suffer for preaching that very doctrine which he has been hitherto employed in persecuting. Strange change indeed! And with great show of reason, as with incontrovertible strength of argument, has a noble writer, Lord Lyttleton, adduced the conversion of Saul of Tarsus, and his subsequent conduct, as an irrefragable proof of the truth of Christianity.

Some think that the words, I will show him, etc., refer to a visionary representation, which Christ was immediately to give Saul, of the trials and difficulties which he should have to encounter; as also of that death by which he should seal his testimony to the truth. If so, what a most thorough conviction must Saul have had of the truth of Christianity, cheerfully and deliberately to give up all worldly honors and profits, and go forward in a work which he knew a violent death was to terminate!

For I will show him ... - This seems to be added to encourage Ananias. He had feared Saul. The Lord now informs him that Saul, hitherto his enemy, would ever after be his friend. He would not merely profess repentance, but would manifest the sincerity of it by encountering trials and reproaches for his sake. The prediction here was fully accomplished, Acts 20:23; 2 Corinthians 11:23-27; 2 Timothy 1:11-12.

9:16 For I - Do thou as thou art commanded. I will take care of the rest; will show him - In fact, through the whole course of his ministry. How great things he must suffer - So far will he be now from persecuting others.