How does one reconcile the changelessness of God with Jesus' incarnation? The Bible says that God "remains the same" (Ps 102:27), and that "Jesus Christ is the same yesterday, today, and forever" (Heb 13:8). This seems to mean that he is changeless.

However, Jesus was not always human. For eternity, he had only a divine nature, up till his physical incarnation, when he gained a human nature as well. He changed from being fully God to being both fully God and fully man (unless one believes that Jesus always had a human nature, even before humans were created).

Correct me if I'm wrong, but for eternity prior to his incarnation, Jesus had no physical body, and then he gained one.

This sounds like a profound change to me.

How is this reconciled with his immutability?
This might be a hard one for us temporal creatures to get our head around, and it actually isn't just the incarnation that poses this problem. Viewed from a temporal perspective, we could just as well say: "Before creation, God wasn't a creator - after creation, he became one. How can this be consistent with the idea of God's immutability?"

The only logical solution to such dilemmas consistent with scripture that I am aware of is that God transcends time itself (ie God's eternity is timeless not everlasting time). From God's perspective in the eternal now, He has always been an incarnated God-man and will always be one. Change (not just in this matter, but in any respect) is something that only occurs within the temporal universe above which, God is transcendent:


  Concepts of eternity have developed in a way that is, as a matter of fact, closely connected to the development of the concept of God in Western thought, beginning with ancient Greek philosophers; particularly to the idea of God's relation to time, the idea of divine perfection, and the Creator-creature distinction. Eternity as timelessness, and eternity as everlastingness, have been distinguished. Following the work of Boethius and Augustine of Hippo divine timelessness became the dominant view. - Stanford Encyclopedia of Philosophy [emphasis added]