What is the biblical basis in the Old Testament for the belief that the Messiah must be God?

Christians believe that Jesus, the Messiah, is God. My question is: What is the biblical basis in the messianic prophecies and other passages in the Old Testament for the belief that the Messiah must be God? I have read this: "https://christianity.stackexchange.com/questions/7531/why-does-the-messiah-have-to-be-god " But I'm looking for the biblical basis in the OT of the belief that Jesus must be God.