35 After this, Matthew goes on with his narrative in these terms: “And leaving the city of Nazareth, He came and dwelt in Capharnaum, which is upon the sea-coast, in the borders of Zabulon and Nephthalim;” and so forth, until we come to the conclusion of the sermon which He delivered on the mount. In this section of the narrative, Mark agrees with him in attesting the calling of the disciples Peter and Andrew, and a little after that, the calling of James and John. But whereas Matthew introduces in this immediate context his account of that lengthened sermon which He delivered on the mount, after He cured a multitude, and when great crowds followed Him, Mark has inserted other matters at this point, touching His teaching in the synagogue, and the people's amazement at His doctrine.
Then, too, he has stated what Matthew also states, although not till after that lengthened sermon has been given, namely, that “He taught them as one that had authority, and not as the scribes.” He has likewise given us the account of the man out of whom the unclean spirit was cast; and after that the story of Peter's mother-in-law. In these things, moreover, Luke is in accord with him. But Matthew has given us no notice of the evil spirit here. The story of Peter's mother-in-law, however, he has not omitted, only he brings it in at a later stage.
Source: The Harmony of the Gospels (New Advent)