I Corinthians 15:14, 58
I Corinthians 15:14 NKJV
And if Christ is not risen, then our preaching is empty and your faith is also empty.
I Corinthians 15:58 NKJV
Therefore, my beloved brethren, be steadfast, immovable, always abounding in the work of the Lord, knowing that your labor is not in vain in the Lord.