Theophylact of Ohrid
Catena Aurea · Markusevangelium 9
And as they came down from the mountain, he charged them that they should tell no man what things they had seen, till the Son of man were risen from the dead. And they kept that saying with themselves, questioning one with another what the rising from the dead should mean. And they asked him, saying, Why say the Scribes that Elias must first come? And he answered and told them, Elias verily cometh first, and restoreth all things; and how it is written of the Son of man, that he must suffer many things, and be set at nought. But I say unto you, That Elias is indeed come, and they have done unto him whatsoever they listed, as it is written of him.
Now the Lord puts this forward to oppose the notion of the Pharisees, who held that Elias was the forerunner of the first advent, shewing 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 isnot 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.