Matthew
Matthew 17:12ESV·traditional attribution

But I tell you that Elijah has already come, and they did not recognize him, but did to him whatever they pleased. So also the Son of Man will certainly suffer at their hands.”

Matthew Henry Presbyterian @wholebiblehenry

We have here the story of Christ's transfiguration; he had said that the Son of man should shortly come in his kingdom, with which promise all the three evangelists industriously connect this story; as if Christ's transfiguration were intended for a specimen and an earnest of the kingdom of Christ, and of that light and love of his, which therein appears to his select and sanctified ones.

Commenting on Matthew 17:1-13

John Gill Reformed Baptist @doctorgill

But I say unto you,.... A way of speaking used by Christ, when he opposes and contradicts any of the tenets of the Scribes and Pharisees; see Mat 5:22 "that Elias is come already"; the person that was signified by, and prophesied of, under the name of Elias: for Christ refers not to the late appearance of Elias on the mount, but to the coming...

Albert Barnes Presbyterian @notesbybarnes

Verse 12. Elias is come. That is, John the Baptist has come, in the spirit and power of Elias. See . They have done whatsoever they listed. The word list is an old English word, signifying to choose, to desire, to be inclined. See . It means here, that they had done to John as they pleased; i.e., they had put him to death, .