“The hope that Christian giving will lead to material prosperity (as divine compensation) derives from a selfish materialism that Scripture regularly rebukes (e.d., 1 Tim 6:9-10). This is not to deny the biblical promises that God rewards generosity (Prov. 11:25; Luke 6:38) but rather to emphasize that only unselfish giving is rewarded. The ironic teaching of Jesus is, essentially, “Expect nothing in return, and your reward will be great” (Luke 6:35; cf. 14:14).”
Mark Alan Powell, “Generosity” in Dictionary of Scripture and Ethics, gen. ed. Joel B. Green (Grand Rapids: Baker Academic, 2011) 324.