Midrash Cohen

"Elijah says to Messiah: "Bear the suffering and punishment of thy Lord with which he chastises thee for the sins of Israel, as it is written, 'He is pressed for our rebellion ­ crushed for our iniquities' until the end come"

Maimonides

Regarding the mission by which Messiah will present himself, ...he will not commend himself to our veneration by reason of his noble extraction; but the marvelous deeds he perform will show him to be the anticipated Messiah...Isaiah states, "He grew like a tender plant, and as a root out of dry land, "signifying, that his exact descent will not be known, till his successful career will direct people's attention to it...But a noteworthy circumstance will be that crowned heads will stand amazed...So they will come in utter silence, as Isaiah predicts, "At him will kings shut their mouths, for what had not been told unto them shall they see, and what they never heard they understand.

Tanchuma, Babylonian Talmud

Rabbi Nahman says, the word "man in the passage...refers to the Messiah, the son of David, as it is written, "Behold the man whose name is Zemah"; there Jonathan interprets, Behold the man Messiah: as it is said, "a man of pains and known to sickness."