Now he who supplies seed to the sower and bread for food will also supply and increase your store of seed and will enlarge the harvest of your righteousness. You will be made rich in every way so that you can be generous on every occasion, and through us your generosity will result in thanksgiving to God. This service that you perform is not only supplying the needs of God’s people but is also overflowing in many expressions of thanks to God. Because of the service by which you have proved yourselves, men will praise God for the obedience that accompanies your confession of the gospel of Christ, and for your generosity in sharing with them and with everyone else. 2 Corinthians 9:10-13
“Generous giving is one of many evidences that someone is truly a Christian. Paul’s point is that if someone has truly received the generous grace of the gospel of Jesus Christ, he or she will be generous. Conversely, if someone is not generous, it may be because he or she does not understand grace and has not received the gospel of our generous Lord Jesus Christ.”
Mark Driscoll and Gerry Breshears in Doctrine: What Christians Should Believe (Wheaton: Crossway, 2010) 395-396.