How do we know our labor is not in vain in the Lord?

In 1 Corinthians 15:58, Paul assures believers that their labor in the Lord is not in vain. This conviction is based on the sovereignty of God, who works all things according to the counsel of His will. When we engage in work that aligns with God's mission, we can be confident that it will produce fruit. As Isaiah 55:11 states, God's word accomplishes the purpose for which it is sent. This encourages us not to grow weary or discouraged but to continue laboring with confidence that God uses our efforts for His glory and the good of His people.