"Therefore, my beloved brothers, be steadfast, immovable, always abounding in the work of the Lord, knowing that in the Lord your labor is not in vain" (1 Corinthians 15:58). These words constitute a great call to the Christians in Corinth; indeed, they are a great call on every Christian. Within this one verse, there are three things to "be" and one to "know".
First, be steadfast. In other words, be settled, be firm, and stay steady. Don't waver. Don't be fickle. Don't veer off the course of Christian belief or Christian living for even one moment.
Second, be immovable. Be a rock. Be a tree with strong, deep roots. As the winds of doctrine blow all around you, refuse to budge from the truth. As the current of cultural morality moves in its own direction, don't go with the flow.
Third, be always abounding in the work of the Lord. Don't just hang on; take ground. Don't just do the work of the Lord; abound in it. Go over and above meager expectations. Invest in your children. Minister to fellow Christians. Reach out to unbelieving neighbors. Give generously. Flourish, thrive, abound!
And what are we to know? Know that your labor is not in vain. Christian faith is not in vain. Christian living is not in vain. Abounding in the work of the Lord is not in vain. Pouring ourselves out for the sake of others is not in vain.
But how can we have confidence that living this way isn't in vain? How can we know we're not just chasing the wind? How can I be sure I'm not wasting my breath and my life? How can I have certainty that my faith isn't just a bit of Karl Marx's 'opium for the masses'? Creating a mere illusion of comfort?
The answer comes by thinking about the first word in the verse: therefore. Paul's call to unshakable living and service doesn't stand on its own. It stands on what comes prior this verse. It stands on chapter 15 as a whole. It stands on the resurrection of Jesus.
We can know that steadfast, immovable faith and abundant work are not in vain because Jesus was raised from the dead. Confidence lies nowhere else.
We don't need self-confidence to live for Jesus. We don't need "new-self-confidence" to live for Jesus (i.e., confidence in who I am in Christ). What we need is Christ-confidence! By faith, we must look to our crucified and risen Savior if we are to live with confident assurance that our lives of faith are not futile.