The attribute of omniscience, of knowing all things, must be clarified. Christian belief holds that God is timeless. Past, present and future for God can be seen as a whole. God also knows how things would turn out if a different path had been taken at every potential choice-making nexus. Furthermore, a 'prophet' in the Bible meant more than simply 'a predictor of the future'. A prophet was also a messenger and an exhorter. His words were never set in stone. A key verse for this is Jeremiah 18:7-10. With this verse, and the fact that the role of a prophet was more than just as a predictor, it is quite clear why it is pointless to object when God withholds judgment. Following ancient rules of rhetoric and the constraints of oral communication, as well as the nature of the Semitic mindset which typically expressed itself in extremes, it would be less appropriate for a prophet making a popular declaration to delineate possible exceptions in his general proclamation. Such side-tracking would make his message less memorable and effective in an era when retention and effect was far more important in the short term than detailed analysis. Finally, to say that God does not 'change' does not mean that God is static, never does anything, or never says anything. Nor can it be asserted to mean that God does not alter stated plans in reaction to human freewill choices. The references to God not 'changing' cannot hold up such a narrow interpretation.

Malachi 3:6 is a 'no change' verse. 'Change' does not refer to simply any possible change, but has specific contexts. Here, it is said in the context of maintaining the covenant promise of preservation to the Israelites in spite of their sins. A covenant agreement is a serious thing — it is a written contract. This was an unconditional promise, unlike those under the Jeremiah 18 clause, and God will not break it, and has not (though the Israelites did).

The Christian doctrine concerning Jesus’ two natures is called the hypostatic union. It is the teaching that the Divine Word of God (John 1:1) "became flesh and dwelt among us," (John 1:14). Therefore, Jesus is both divine and human in one person (Col. 2:9); He has two natures: human and divine. But some who oppose the Trinity and Jesus’ incarnation (the Divine Word becoming a man), say that if Jesus is God in flesh, this must mean that God’s nature changed because God added a human nature to His divine nature. This would violate Malachi 3:6 which says that God does not change. But, the union of the two natures of Jesus in one person does not constitute a change in the nature of God.

Since the hypostatic union teaches that in the one person of Jesus there are two natures, the divine nature of Jesus is not affected by union with the human nature because there is no fusion of the two natures. That is, the divine nature is not combined with the human nature to make a third thing. This would be the error known as monophysitism. Jesus is not a new third thing with a fused-together new nature. Instead, it is a union. An example of a union is marriage between a man and a woman. Each is separate, but in marriage "…they shall become one flesh," (Gen. 2:24), yet they remain two distinct individuals. They are not blended into a new third thing. Fusion, on the other hand, can be illustrated by combining copper and zinc together to form a new third thing called brass. In this case, the two elements lose their identity and are merged together into something new. But in a union, the elements do not lose their identity or nature. The hypostatic union is not a hypostatic fusion. The two natures of Jesus do not lose their distinction, and they are not altered.

Furthermore, within the union of the two natures in the one person of Christ, the divine nature is still divine, and the human nature is still human. One is not altered by the presence of the other any more than my spirit in me is altered in nature by its indwelling a physical body. Likewise, the divine Word is not altered by indwelling human flesh.

Finally, the doctrine of the Trinity is that God is three persons: Father, Son, and Holy Spirit. This does not mean three gods. There is only one God. The Trinitarian nature of God is not altered by the union of the Word with humanity since it was the divine Word that humbled Himself to become a man (John 1:1, 14; Phil. 2:5-8), not the Father or the Holy Spirit. Therefore, by definition, the Trinity is unaffected by the union of the Word with humanity in the incarnation of Jesus.