Albert Barnes Commentary Matthew 17:11

"And he answered and said, Elijah indeed cometh, and shall restore all things:" — Matthew 17:11 (ASV)

Elias truly shall first come, and restore all things. He did not mean by this that Elijah was still to come, for He directly tells them that he had come. Rather, He meant to affirm the true doctrine taught by the scribes: that Elijah would appear before the coming of the Messiah.

To restore means to put into the former situation . Therefore, it means to heal, to correct, to put in proper order. Here, it means that Elijah would put things in a proper state, be the instrument of reforming the people, of restoring them, to some degree, to a proper understanding about the Messiah, and preparing them for His coming.

Before the coming of John, their views were erroneous, their expectations worldly, and their conduct exceedingly depraved. He corrected many of their erroneous ideas about the Messiah (Matthew 3:1) and was the instrument of an extensive reformation. Thus, he restored them, to some degree, to a correct understanding of their own religious system and of the Messiah, and to a preparation for His advent.