1 Corinthians 9:10

9:10 Or is he not surely speaking for our benefit? It was written for us, because the one plowing and threshing ought to work in hope of enjoying the harvest.

1 Corinthians 15:58

15:58 So then, dear brothers and sisters, be firm. Do not be moved! Always be outstanding in the work of the Lord, knowing that your labor is not in vain in the Lord.