God is love. Love is only complete when the power of choice is available. Let me give you an example. Let's say a man falls in love with a woman. He locks her in his house. Even if he treats her well, if he never gives her the right to choose whether or not to stay with him; he has not manifested true love.
God demonstrated His love by allowing Adam and Eve to choose whether they wanted to love him back or not. He warned them not to eat from the tree of the knowledge of good and evil. They had thousands of other trees from which to eat delicious fruit. If they chose to disobey they would cut off their life source and die.
Eve left Adam's side. Satan appeared to her as a beautifully colored snake. He said to her, "You shall not die, you will become as smart as GOD." Eve chose to disbelieve God; she chose to reject his warnings of love and she did not manifest the love of obedience.
Adam chose to love Eve more than God and disobeyed also. They came to know evil, they came to know what it was like to be cut off from the source of love. They learned that feelings of guilt and shame accompany evil. For the first time they experienced fear and ran away from God.
But God still manifested love. God went running after them, calling them to come back to Him. He allowed them to sacrifice a clean animal, representing the death to evil they would have to experience and the death that the Messiah would have to die to take their evil away and give them another chance. God then used the skin of those animals to cover their nakedness. Now they were clothed in the Messiah’s righteousness and He would now give them the power to obey. God is love.
Picture originally found here