In 1 Corinthians 15:58, Paul urges believers to be what?

Answer: Steadfast and immovable

Be steadfast and immovable, always excelling in the work of the Lord, because your labor in the Lord is not in vain.

“Therefore, my beloved brothers, be steadfast and immovable. Always excel in the work of the Lord, because you know that your labor in the Lord is not in vain.”— 1 Corinthians 15:58 (BSB)