Giving the firstfruits of our income to the Lord in the right spirit is an act of faith. “Without faith it is impossible to please Him, for he who comes to God must believe that He is, and that He is a rewarder of those who seek Him” (Hebrews 11: 6). The Lord requires faith before He will release His power toward us. Giving our firstfruits to Him is an act of faith by which we are declaring that we trust Him as the Source of our provision.
From the book "Overcoming Poverty "