God gave his only begotten Son and when you get saved you have the opportunity to serve him. We want to glorify God with every area of our lives, and that includes what we do with our finances. What we do with what God has given us shows where our hearts are at and helps further the gospel.
2 Corinthians 9:7 Every man according as he purposeth in his heart, so let him give; not grudgingly, or of necessity: for God loveth a cheerful giver.