1 Corinthians 15:10 (AMPC)

But by the grace (the unmerited favor and blessing) of God I am what I am, and His grace toward me was not [found to be] for nothing (fruitless and without effect). In fact, I worked harder than all of them [the apostles], though it was not really I, but the grace (the unmerited favor and blessing) of God which was with me.