The Bible says in 2 Corinthians 8:8-9,
8. "I speak not by commandment, but by occasion of the forwardness of others, and to prove the sincerity of your love.
9. For ye know the grace of our Lord Jesus Christ, that, though he was rich, yet for your sakes he became poor, that ye through his poverty might be rich."
God has given us everything. What we do with what God has given us shows the world that we have put our faith and trust in Jesus Christ. We want to glorify God with every area of our lives, and "prove our love" to Him that SO LOVED the world.