John Mark
Mark 9:12ESV·traditional attribution

And he said to them, “Elijah does come first to restore all things. And how is it written of the Son of Man that he should suffer many things and be treated with contempt?

Matthew Henry Presbyterian @wholebiblehenry

Here is, I. A prediction of Christ's kingdom now near approaching, Mar 9:1. That which is foretold, is, 1. That the kingdom of God would come, and would come so as to be seen: the kingdom of the Messiah shall be set up in the world by the utter destruction of the Jewish polity, which stood in the way of it; this was the restoring...

Commenting on Mark 9:1-13

John Gill Reformed Baptist @doctorgill

And he answered, and told them,.... Allowing that their observation was right, and that this was the sense of the Scribes, and that there was something of truth in it, when rightly understood: Elias verily cometh first, and restoreth all things: See Gill on Mat 17:11; and how it is written of the son of man, that he must suffer many things, and be set at nought.

Albert Barnes Presbyterian @notesbybarnes

Verse 12. (y) "written of the Son" (z) "be set"