When comparing the Old Testament and the New Testament of the Bible, there can be the impression that between the two there has been a change in the attitudes of God. The Old Testament, with its records of centuries of battles and confrontation between God and humans, can leave an impression of God's anger and justice. In comparison, the New Testament could be characterised by Jesus' teachings of love and compassion. Initially, the two may seem at odds but a closer analysis of the content of each shows that God is actually quite consistent between the two.
1. Does God Change?
We can learn about the nature of God in both the direct and indirect writings about him in the Bible. In terms of the direct descriptions, there are a number of sections of the Bible that directly state how God is unchanging, both in the Old and New Testament.
James 1:17 : Every good gift and every perfect gift is from above, coming down from the Father of lights, with whom can be no variation, nor turning shadow. WEB
Psalms 102:27 : But you are the same. Your years will have no end. WEB
Numbers 23:19 : God is not a man, that he should lie, Neither the son of man, that he should repent: Has he said, and will he not do it? Or has he spoken, and will he not make it good? WEB
Malachi 3:5 : I will come near to you to judgment; and I will be a swift witness against the sorcerers, and against the adulterers, and against the perjurers, and against those who oppress the hireling in his wages, the widow, and the fatherless, and who deprive the foreigner of justice, and don't fear me,” says Yahweh of Hosts. 6. “For I, Yahweh, don't change; therefore you , sons of Jacob, are not consumed.” WEB
The assertion is that God's plans and promises remain constant. There is a sense that we can have a certainty in God. What is good and what is evil is an unchanging truth defined by God.
Foreknowledge Of God
An aspect associated with God's steadfastness is his knowledge of the future. If the course of the world was already laid out in front of God, then there would be no reason to change his attitudes in response to the events as they occur. His emotional reaction would instead occur right at the time of creation when he knew of that future.
This rationale is cited in Romans to explain why God couldn't have rejected his nation of Israel. Paul there writes that God knew the response of his people, and that the promises were given regardless.
Romans 11:1: I ask then, Did God reject his people? May it never be! For I also am an Israelite, a descendant of Abraham, of the tribe of Benjamin. 2. God didn't reject his people, which he foreknew. Or don't you know what the Scripture says about Elijah? How he pleads with God against Israel: WEB
The argument follows that God's promises are sure, because he has already taken into account all of the eventualities that the future will turn up.
Of particular significance to any changes between the Old and New Testaments is the appearance of Jesus. That was the defining event that triggered the events recorded in the New Testament. However, the scriptures are clear that the appearance of Jesus was no surprise to God. It was the culmination of a plan of redemption he had had right from the time of the sin of Adam and Eve in Eden.
In the promises given to Abraham right near the start of the Bible, Jesus was referred to directly as a descendent who was to be a blessing to all nations (confirmed in Gal 3:16).
Genesis 22:18 : In your seed will all the nations of the earth be blessed, because you have obeyed my voice.” WEB
As a part of that blessing, God had determined the role that Jesus was to take, including his death on the cross. The mode of salvation for humans had already been determined by God, so to an extent to God the event had already happened because it was assured to take place. In the preaching of the apostles soon after the ascension of Jesus into heaven, Peter stated how God knew in advance of the events that had happened.
Acts 2:22: Men of Israel, hear these words! Jesus of Nazareth, a man approved by God to you by mighty works and wonders and signs which God did by him in the midst of you, even as you yourselves know, 23. him, being delivered up by the determined counsel and foreknowledge of God, you have taken by the hand of lawless men, crucified and killed; WEB
Jesus understood how his own role in life was already mapped out by God. He knew that God had already known of his life right back before those promises were given to Abraham. When speaking to the Jews, he expresses how both God and Abraham has the assurance of his life and work some 2000 years previously. Because of this assurance, it was as if he already existed to them back at that time. Jesus spoke to the Pharisees of this,
John 8:56: Your father Abraham rejoiced to see my day. He saw it, and was glad.” 57. The Jews therefore said to him, “You are not yet fifty years old, and have you seen Abraham?” 58. Jesus said to them, “Most assuredly, I tell you, before Abraham came into existence, I AM.” WEB
To God, the sense of time is not so important as it is to us. For him. because of his knowledge of future events, he doesn't need to wait for events to happen to see their reality, or to respond. Consequently, there would be little reason to expect a dramatic change in the character of God through the process of time, or with specific events, such as the birth of Jesus.