In his book, The Deep Things of God: How the Trinity Changes Everything, Fred Sanders suggests that the Trinity is the basis for grace. Grace is unmerited favor. In the words of A.W. Pink, grace is "favor shown where there is positive demerit in the one receiving it.” The things that makes God's grace so amazing is that he gave it when he had absolutely no need. Nothing outside of him compelled him. The Trinity is the reason we can make this statement.
God did not create and redeem us because he needed friendship. He had the other members of the Trinity to relate to from all eternity. His social needs were filled to the brim. He did not create us because there was any lack in his happiness or joy. The other members of the Trinity brought infinite delight to each other. God was completely happy and satisified. So why did God create? He does all things for his glory. He acts to share his happiness (his glory) with his creatures. He creates to see his glorified exercised so that he can further delight in it. The one thing he did not do was act from need.
Because of the reality of the Trinity “God did not have to save us," Sanders observes. "There was no external necessity imposed on him, nor did he have any internal need. The perfect blessedness of God would not have been compromised by the final failure of humanity. God did not save us to rescue himself from sadness over our plight. He saved us freely, out of an astonishing abundance of generosity…God created freely and also redeemed freely” (Pg 65).
This is impossible for us to understand. We are creatures. Need motivates everything we do. We are God's opposite. We are infinitely incomplete and needy. God created our need to be met by himself. Even our love for God is tainted by our need for God. But God loves without need. He gives himself without reference to any personal gain.
Contemplate this in light of the cross, an act of love, suffering, and deprivation for the good of others without paralell. On thing is clear. God is not like us. He is holy, and his holiness expresses itself most perfectly in his love for uworthy sinners, i.e. through the grace that is unmerited favor and that rests on a Trinitarian foundation.