The Sages have said:

What is the cause of the mourning (Zechariah 12:10)? It is well according to him who explains that the cause is the slaying of Messiah, the son of Joseph, as it is written, 'And they shall look upon me whom they have pierced; and they shall mourn for him as one mourneth for his only son.'

Babylonian Talmud

Babylonian Talmud, Sukkah 52a

The Sages have said:

I may remark then, that our Rabbis with one voice accept and affirm the opinion that the prophet is speaking of the King Messiah, and we ourselves shall adhere to the same view.

Rabbi Mosheh El-Sheikh

[Rabbi Mosheh El-Sheikh regarding Yesha’yahu 53 in the Tanakh]