Have you ever wondered why God would have us give our stuff away? Greed and materialism run rampant in today's culture as they have in just about any culture across the globe and throughout history. God hates greed and materialism because they rob us of the abundant life He wants us to have. Hording money will not buy us freedom in life - it actually buys us slavery to possessions. Generosity is the only way to experience life as God intended us to.
"Command them to do good, to be rich in good deeds, and to be generous and willing to share. In this way they will lay up treasure for themselves as a firm foundation for the coming age, so that they may take hold of the life that is truly life." 1 Timothy 6:18-19
Giving also helps combat legalism. Legalism is a noose that can slowly tighten around a Christ follower's neck and choke the life right out of him. We're being legalistic in our giving when we do so out of a guilty conscience. God doesn't want us to give because we think he's going to zap us if we don't; he wants us to give because we truly want to give. Greedy people sometimes give more money than anyone, but they experience less life because they do it out of guilt; generous people give because they love God, they love those in need, and they want be just like Jesus. God is not interested in the simple action of giving; he is intensely interested in the faith that prompts the action of giving.
"Each man should give what he has decided in his heart to give, not reluctantly or under compulsion, for God loves a cheerful giver." 2 Corinthians 9:7