Tithes and Offerings
Giving is an expression of our thankfulness and praise to God. It comes from a heart of worship that recognizes everything we have and give already belongs to the Lord.
God instructed Old Testament believers to give a tithe, or a tenth because this ten percent represented the first, most important portion of all they had. The New Testament does not suggest a certain percentage for giving, but simply says for each to give "in keeping with his income."
Everything we own and everything we have comes from God. So, when we give, we simply offer him a small portion of the abundance he has already given to us.