1 Corinthians 15:10 (ESV)

10 But by the grace of God I am what I am, and his grace toward me was not in vain. On the contrary, I worked harder than any of them, though it was not I, but the grace of God that is with me.

Paul sees God’s grace at work in his life, from his birth to his ministry as apostle (see Galatians 1:15; Ephesians 3:7–8). Note that he writes, By the grace of God I am what I am and not, “By the grace of God I am who I am.” His focus is not on himself as a person, but on himself as an apostle: an instrument in God’s hand for the spreading of the gospel.

God has shown grace toward Paul—in other words, to him individually. This grace has not been in vain, but it has reached its goal of transforming Paul into an instrument for God’s glory. Paul goes so far as to say that he worked harder than all the other apostles. Although we do not have detailed information about the work of the other apostles, it is hard to imagine that anyone could travel more, plant more churches, write more, and suffer more for the gospel than Paul did.

Yet Paul is not prideful. At the end of this verse he uses the word grace for the third time. This time he is testifying to God’s empowering grace. God’s grace is with him as he does the work of an apostle (see also Ephesians 3:7).