In 2 Corinthians 9:6-7, Paul explains to us how important cheerful, generous giving is. As it says, "Whoever sows sparingly, will also reap sparingly, and whoever sows bountifully, will also reap bountifully."
But this isn't just with money. It's bigger than that! In verse 7, Paul explains that this is of the heart. Offering our tithes to God is an act of Worship. By doing so, we're declaring with our hearts that God is not only the ruler of our lives, but of our finances as well.