Some of us like to give hints to see if the recipient of our gift can guess what’s inside. It builds the anticipation. That’s what God did. Centuries before offering us the gift of His Son, Jesus, He gave “hints” to the prophets of Israel concerning the coming of the Messiah. One of those prophets was Isaiah. God gave Isaiah many of the over 300 Messianic prophecies found in the Old Testament.
In Isaiah 9, God gave him a Messianic prophecy of a promised Son that would be given. We can recognize that Jesus is the promised Son that would be given. He is the Son of God given unto us.