You must tithe all the produce of the seed that the field yields year by year.
Devarim 14:22
This verse includes the instruction to donate a portion of our income to charity. The Talmudic sages pointed out that the similarity of the Hebrew words for "tithe" (ta'aseir) and "become rich" (titasheir) alludes to the fact that G-d rewards those who give charity with abundant wealth.
Furthermore, when we resolve to give charity beyond our means, G-d grants us the wealth that is required in order for us to give the charity we resolved to donate.
--From Kehot's
Daily Wisdom