Acts 8:13

Then Simon himself believed also
With an historical and temporary faith, as that Jesus was the Messiah 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.