to bring glory to God as His glorious children
God created man and woman in His own image and so made Adam and Eve very glorious. Just looking at the delicate weaving together of our flesh and bone, understanding the complex chemical processes, considering the language of genetics - it is awesome.
But sin destroyed the original glory of man. Rebellion marred the creation of God.
Now, it must be understood that God is just; He cannot tolerate sin (Psalm 92:15). Man's sin separated him from God (Genesis 3:24). And this did not please God. To Ezekiel, God said, "I take no pleasure in the death of anyone..." (Ezekiel 18:32) God created us in His image and with a purpose - He does not want us to live broken lives subjected to fear and death.
So, what could God do?
He wanted to reconcile people to Himself, but He cannot tolerate sin. So, he offered people the opportunity to gain right standing before Him through the Law of Moses. The Law tells us how to live pure and just lives that are acceptable to God. Unfortunately, we as humans cannot live up to the high standard of the Law. We cannot become righteous by our effort.
So, what could God do?
Romans 8:3-4 "what the Law could not do, weak as it was through the flesh, God did: sending His own Son in the likeness of sinful flesh and as an offering for sin, He condemned sin in the flesh, so that the requirement of the Law might be fulfilled in us, who do not walk according to the flesh but according to the Spirit." God sent His Son as the sacrifice that purifies our sin and then sent His Spirit to live in us and help us to live righteously day by day.
Now, the children of God await the day when God's plan will be ultimately fulfilled. "...we wait eagerly for our adoption as sons, the redemption of our bodies" (Romans 8:23). As Christ was raised in glory and took on a new, resurrection body, so too will the other children of God. We will be glorified once again, even as man and woman were in the beginning. God will dwell with His people forever and "make all things new" (Revelation 21:5). This is God's will. That one day His children will reign with Him in glory - the glory with which He created them in the beginning - and they will live with Him and worship Him as God.
God did the work. All we need to do is accept it and live by this truth. This is what faith is. Faith is trusting it to be true and living by this hope.
(John 5:24, John 17:3, John 3:18)