In chapter 3 of his first letter to the Corinthians, Paul describes the work of building the church: “If anyone builds on the foundation with gold, silver, costly stones, wood, hay, or straw, each person’s work will be revealed for what it is. The Day will declare it, because it is revealed in fire, and the fire itself will test what sort of work each person’s work is. If anyone’s work survives, that person will receive a reward. If anyone’s work is burned, that person will suffer loss.”
Paul’s encouragement is for those who are involved in the gospel work to make sure they build something substantial, which will withstand the coming fire, rather than something insubstantial, which will be burned up. However, this must be taken in tension with Paul’s earlier statement discounting the importance of the workers: “The one who plants and the one who waters are nothing, because only God causes the growth.”
There seems to be a contradiction between the idea that the person who builds something that lasts will receive a reward and the idea that those who plant and water are nothing because only God causes the growth. Perhaps the tension is best resolved by concentrating on the building, rather than the reward. Someone who is in it for the reward may not have the right motive when building.