John Gill

Then Simon himself believed also,.... With an historical and temporary faith, as that Jesus was the Messiah, &c. or at least he pretended, to believe this, and professed that he did believe, what others did, and Philip preached: and when he was baptized; upon profession of his faith, which he so artfully made, that Philip could not discover his hypocrisy: but taking him to be a sincere believer, admitted him to baptism: after which, he continued with Philip; kept close to him, and got into a familiar acquaintance with him; and constantly attended on his ministry, as if he had been a sincere disciple and follower of Christ: and wondered, beholding the miracles and signs which were done; he was as much amazed at the miraculous performances of Philip, as the inhabitants of Samaria had been at his, which he could observe were real things; and this increased his wonder, and threw him into an ecstasy, that he was scarce himself: whereas he knew that what he did were only sham performances, and legerdemain tricks.