In Christ our giving already brings a reward! 

2 Corinthians 9:6-11
Remember this: Whoever sows sparingly will also reap sparingly, and whoever sows generously will also reap generously. 7 Each man should give what he has decided in his heart to give, not reluctantly or under compulsion, for God loves a cheerful giver. 8 And God is able to make all grace abound to you, so that in all things at all times, having all that you need, you will abound in every good work. 9 As it is written:
“He has scattered abroad his gifts to the poor;
his righteousness endures forever.”
10 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. 11 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.

Philippians 4:14-19
Yet it was good of you to share in my troubles. 15 Moreover, as you Philippians know, in the early days of your acquaintance with the gospel, when I set out from Macedonia, not one church shared with me in the matter of giving and receiving, except you only; 16 for even when I was in Thessalonica, you sent me aid again and again when I was in need. 17 Not that I am looking for a gift, but I am looking for what may be credited to your account. 18 I have received full payment and even more; I am amply supplied, now that I have received from Epaphroditus the gifts you sent. They are a fragrant offering, an acceptable sacrifice, pleasing to God. 19 And my God will meet all your needs according to his glorious riches in Christ Jesus.