1 Corinthians 9:11 says that if Paul and his fellow workers have shared spiritual blessings or teachings with the Corinthians, it is not unreasonable for them to receive material support in return. The verse uses the idea of sowing spiritual things and reaping carnal (physical or material) things to make this point.
Paul is writing to the church in Corinth, explaining why it is fair for those who teach and serve spiritually to receive practical help from those they serve. He uses a farming metaphor—sowing and reaping—to show that sharing in spiritual work can rightly lead to sharing in material benefits. The verse is part of a larger discussion where Paul defends the rights of apostles but also explains his own choice not to use those rights for the sake of the gospel.