Mark 9:12

(Vict. Ant. e Cat. in Marc.) Or else, the disciples asked Jesus, how it was written that the Son of man must suffer? Now in answer to this, He says, As John came in the likeness of Elias, and they evil intreated him, so according to the Scriptures must the Son of man suffer.

(ubi sup.) Again, He will restore all things, that is to say, those things which Malachi points out, saying, Behold, I will send you Elijah the prophet, and he shall turn the heart of the fathers to the children, and the heart of the children to their fathers; (Mal. 4:5, 6) he will yield up also to death that debt, which by his prolonged life he has delayed to render.

Now the Lord puts this forward to oppose the notion of the Pharisees, who held that Elias was the forerunner of the first advent, showing that it led them to a false conclusion; wherefore he subjoins, And how it is written of the Son of man, that he must suffer many things, and be set at nought. As if He had said, When Elias the Tishbite cometh, he will pacify the Jews, and will bring them to the faith, and thus be the forerunner of the second advent. If then Elias is the forerunner of the first advent, how is it written that the Son of man must suffer? One of these two things therefore will follow; either that Elias is not the forerunner of the first advent, and thus the Scripture will be true; or that he is the forerunner of the first advent, and then the Scriptures will not be true, which say that Christ must suffer; for Elias must restore all things, in which case there will not be an unbelieving Jew, but all, whosoever hear him, must believe on his preaching.