We give because God has given freely to us. In fact, He gave His only begotten Son, the Lord Jesus Christ, as the payment for our sin. "Freely you received, freely give," says Matthew 8:10. So our giving is an act of worship to the Lord and a part of our discipleship as managers of all that God has given to us.
II Corinthians 9:7, "Each of you should give what you have decided in your heart to give, not reluctantly or under compulsion, for God loves a cheerful giver."
Matthew 6:19-21, "Do not store up for yourselves treasures on earth, where moths and vermin destroy, and where thieves break in and steal. But store up for yourselves treasures in heaven, where moths and vermin do not destroy, and where thieves do not break in and steal. For where your treasure is, there your heart will be also."