Albert Barnes on Acts 4:14

They could say nothing, etc. The presence of the man that was healed was an unanswerable fact in proof of the truth of what the apostles alleged. The miracle was so public, clear, and decisive; the man that was healed was so well known, that there was no evasion or subterfuge by which they could escape the conclusion to which the apostles were conducting them. It evinced no little gratitude in the man that was healed that he was present on this occasion, and showed that he was deeply interested in what befell his benefactors. The miracles of Jesus and his apostles were such that they could not be denied; and hence the Jews did not attempt to deny that they wrought them. Comp. Mt 12:24, Jn 11:45,46; Acts 19:36.

(+) "healed" or "cured" (b) "say nothing" Acts 19:36