John Chrysostom — as excerpted in the Catena Aurea on John 2:1-4

“(Hom. xxi. 1, 2) But how came it into the mother’s mind to expect so great a thing from her Son? for he had done no miracle as yet: as we read afterwards, This beginning of miracles did Jesus. His real nature, however, was beginning now to be revealed by John, and His own conversations with His disciples; besides that His conception, and the circumstances of His birth, had from the first given rise to high expectations in her mind: as Luke tells us, His mother kept all these sayings in her heart. (Luke 2:51) Why then did she never ask Him to work a miracle before? Because the time had now come that He should be made known. Before He had lived so much like an ordinary person, that she had not had the confidence to ask Him. But now that she heard that John had borne witness to Him, and that He had disciples, she asks Him confidently.”