God was not changed by the incarnation; the Word (logos) was made flesh, not by a conversion of the Word (tou logou) into flesh, but by an assumption of the flesh to the hypostasis of the Word (logou). It is one thing to change the will; another to will the change of anything. God can will the change of various things (as the institution and abrogation of the Levitical worship) without prejudice to the immutability of his will because even from eternity he had decreed such a change.
Anselm famously stated that God is “that being of which there is none greater.” The members of the Westminster Assembly explained that God is “a Spirit, infinite, eternal, and unchangeable in His being, wisdom, power, holiness, justice, goodness and truth.” The living and true God is an infinite and eternal being. He is also a personal and communicative being. The Triune God reveals Himself and His will to His creatures in His word so that they might truly know Him in Christ (John 17:3). All that God has revealed about Himself in Scripture, He has revealed in human language. He reveals Himself and His ways to us by means of “anthropomorphic” terms (i.e. human forms) and “anthropopathic” terms (i.e. human emotions) so that we can understand. This makes our limited understanding of the incomprehensible God really possible. However, it also requires us to make sharp distinctions based on literary forms and systematic theological categories. Such is the case in the language of God.
When we consider the anthropomorphic and anthropopathic language of Scripture we must be clear that these are simply accommodations. God does not and cannot change. No change in God is brought about by things outside of Him. God is not caught off guard by the actions of His creatures. God does not learn anything from His creatures. Rather, God has–as the Westminster Confession of Faith states–“foreordained whatsoever comes to pass.” God stands outside of time, even as He works His eternal plans out in time and space. The immutability (i.e. unchangeableness) of God gives believers the strongest consolation that nothing will keep Him from fulfilling His promises (Mal. 3:6; Heb. 6:17–18).
Nevertheless, God is personally involved in all of His creation in accord with His own character and attributes. Believers commune with the living God in prayer and worship. God disciplines us out of His love for us (Heb. 12:3–11). God indwells and empowers believers by His Spirit–causing Christ to be formed in us (Eph. 3:17; Col. 1:27; Gal. 4:19). The Lord intervenes in our lives to bring about His will (Heb. 13:21). We can do things that anger God, and we can do things that please Him (Mic. 7:18; 2 Cor. 5:9).