Albert Barnes on Matthew 14:2

This is John the Baptist. Herod feared John. His conscience smote him for his crimes. He remembered that he had wickedly put him to death. He knew him to be a distinguished prophet; and he concluded that no other one was capable of working such miracles but he who had been distinguished in his life, and who had again risen from the dead, and entered the dominions of his murderer. The alarm in his court it seems was general. Herod's conscience told him that this was John. Others thought that it might be the expected Elijah, or one of the old prophets, Mk 6:15.

(1) "mighty" or, "are wrought by him"