The hearers could hardly believe what they were seeing. Barnes says they were "amazed at his sudden and remarkable change." They knew Saul's reputation and why he had come to Damascus: to arrest people who called on Jesus' name. Now he was calling others to that name. Matthew Henry pictures the astonishment with the Latin saying "Quantum mutatus ab illo," which he renders "Oh how changed!" and he echoes the old question, "Is Saul also among the prophets?" (1 Samuel 10:11). Their question was not a request for information. It was wonder at a change too great to explain.

No one answers them in words. Saul's life answered instead: "But Saul increased the more in strength, and confounded the Jews which dwelt at Damascus, proving that this is very Christ" (Acts 9:22). The change was real, and it cost him. After many days the Jews took counsel to kill him, and the disciples let him down by the wall in a basket (Acts 9:23-25).

Saul had come with letters from the high priest to the synagogues of Damascus, to bring any followers of Jesus "bound unto Jerusalem" (Acts 9:2). Even Ananias had heard that he had "authority from the chief priests to bind all that call on thy name" (Acts 9:14).

The word "destroyed" translates the Greek porthesas, which the BibleHub interlinear glosses "having ravaged." Barnes explains it as "opposed; laid waste; or persecuted." Paul uses the same verb about himself in Galatians 1:23: the churches heard that "he which persecuted us in times past now preacheth the faith which once he destroyed."

The question the Damascus hearers asked is the question the whole Saul story raises: can someone really change this much? The surrounding text says yes, and it shows God as the One who did it. The man who came to bind "all that call on thy name" (Acts 9:14) was himself told to be baptized, "calling on the name of the Lord" (Acts 22:16).

Matthew Henry notes that many took it as a great confirmation of Christianity that a man who had been "such a notorious persecutor" became, on a sudden, "such an intelligent, strenuous, and capacious preacher." Paul later told the Galatians how the churches responded when they heard of this change: "they glorified God in me" (Galatians 1:24). The glory went to God, not to Saul.