God, changes not.
The Bible says God is light and God is love. God is perfect. These attributes don't change. His judgement is just and he is merciful to those that call upon His name. That doesn't change. When he gave the law as in the old testement, He did so out of love for his creation. It was for their safety and benefit to follow those laws. Then in the New testament when God's only begotten son living a sinless life, fullfilled all the law, and took upon Himself all the sins of the world, the situation changed. BUT God did not change. He still is love and light and judges righteously. Only the circumstances changed to allow more of His love to abound, thanks to Jesus death and resurrection.
People don't realize that God put limits and boundaries on Himself by giving His word. He cannot lie or break His word. So in a sense, he is bound by His word, or honors His word. So when He gave dominion of this world to man, and man sinned and bowed to the deceiver Satan, God, still had to honor his Word to man. Man was given dominion of God's creation and God had to send His son in the Flesh to redeem man because of His word. He couldn't just take Satan out, because God gave dominion to man-Human Flesh. And
God is a Spirit. Satan took dominion from man illegally as a spirit being himself and did it with deception. God was not going to go against His word, therefore God had to be made flesh. The legal entrance to this earth is being born of a woman. The illegal entrance to this earth is what Satan accomplished as a spirit. He did not enter by human birth. Jesus did and was therefore not in violation of the word that God spoke concerning man having dominion. God gave it to man. Satan decieved it away from man. And God in the flesh, Jesus, got it back.
John 10 Brackets mine.
1 "Most assuredly, I say to you, he who does not enter the sheepfold(EARTH) by the door(BORN OF A WOMAN), but climbs up some other way(AS IN SATAN AS A SPIRIT BEING), the same is a thief and a robber(SATAN). 2But he who enters by the door(JESUS-being born of a woman) is the shepherd of the sheep. 3To him the doorkeeper opens, and the sheep hear his voice; and he calls his own sheep by name and leads them out. 4And when he brings out his own sheep, he goes before them; and the sheep follow him, for they know his voice. 5Yet they will by no means follow a stranger, but will flee from him, for they do not know the voice of strangers." 6Jesus used this illustration, but they did not understand the things which He spoke to them.
7 Then Jesus said to them again, "Most assuredly, I say to you, I am the door of the sheep. 8All who ever came before Me[1] are thieves and robbers, but the sheep did not hear them. 9I am the door. If anyone enters by Me, he will be saved, and will go in and out and find pasture. 10The thief does not come except to steal, and to kill, and to destroy. I have come that they may have life, and that they may have it more abundantly.
This might be long winded to some but it illustrates that God CANNOT go against His word, and why He redeemed man, in the manner that He did is because of honoring His word to man. Satan does things illegally, but God does not. That is why between the Old and New Testament God seems to be different. It is rather that after redeeming man, both Sinful man and Satan are not limiting God's Grace and mercy by the same structured LAW. But rather the Law is now summed up as "Love the Lord God, and Your neighbor as yourself".
God didn't change, only the circumstances allowing God to demonstrate more Love, Mercy, and Grace.
A believer in the God of Miracles, who changes not. In Jesus my Lord and Savior, the same yesterday, today, and forever.