God doesn’t save people because He must, He saves people because He delights to do so. Paul is a wonderful example:
But when he who had set me apart before I was born, and who called me by his grace, was pleased to reveal his Son to me, in order that I might preach him among the Gentiles, I did not consult anyone. – Galatians 1:15-16
Why would God save someone like Paul who formerly was a persecutor of the church and a murderer? Because it pleases Him to do so. Yes, God demonstrates his love for us in that “while we were yet sinners, Christ died for us” (Romans 5:8). This love surely is not an unaffected love. Surely this love is moved by more than duty. In fact if we were to say that the cross was motivated by duty, we would be bringing Christ down! No, Jesus endured the cross for the “joy set before Him” (Hebrews 12:2). No doubt the cross was painful beyond all comprehension, but even in the midst of the full weight of God’s wrath being poured out on the Son, Jesus was nonetheless displaying the most profound love for sinners imaginable.
I firmly believe the Jesus’ primary motive in going to the cross was to bring glory to the Godhead (John 17:1-2; Phil 2:9-11; Ephesians 2:7). However, we must never forget that real love for real sinners was being powerfully expressed on the cross. What is most central to the cross is the glory of God being shown forth in this act of love, but nonetheless the cross was the greatest act of love in the history of the universe and its love worth boasting in (Gal. 6:14)–love that ought to give direction to every subsequent act of love (Ephesians 5:25).
C. S. Lewis in his sermon, The Weight of Glory, attempts to express the profundity of the love expressed on the cross like this:
In the end that Face which is the delight or the terror of the universe must be turned upon each of us either with one expression or with the other, either conferring glory inexpressible or inflicting shame that can never be cured or disguised. I read in a periodical the other day that the fundamental thing is how we think of God. By God Himself, it is not! How God thinks of us is not only more important, but infinitely more important. Indeed, how we think of of Him is of no importance except insofar as it is related to how He thinks of us. It is written that we shall “stand before” Him, shall appear, shall be inspected. The promise of glory is the promise, almost incredible and only possible by the work of Christ, that some of us . . . shall actually survive that examination, shall find approval, shall please God. To please God . . . to be a real ingredient in the divine happiness . . . to be loved by God, not merely pitied, but delighted in as an artist delights in his work or a father in a son–it seems impossible, a weight or burden of glory which our thoughts can hardly sustain. But so it is.
The Lord delights to save, not because we are worthy to save but because we are not and His power is made perfect in weakness (2 Cor 12:9). There is great rejoicing in heaven when one sinner repents (Luke 15:7)!