Peah and Leket
"You shall not reap every last edge of your field and not gather in the gleanings of your harvest.. you shall leave them for the poor and the proselyte." (Vayikra 19:9-10)
When reaping his agricultural produce, a Jew is obligated to leave peah a little of that produce at the edge of the field which will be available for the poor and proselyte.
The gleanings those pieces that fall from the sickle during the reaping or from the hand during the picking - must be left behind for the poor and proselyte.
G-d wished that the people He chose be of generous spirit. Mans character is the result of his activities and if he is involved in generosity he will become a good man worthy of G-ds blessing. By leaving behind a part of the produce of his field so that those in need can benefit from it, he will sense spiritual satisfaction and G-d will satisfy him with His boundless goodness.