Thou shall not wholly reap - Leviticus19:9-10
"And when ye reap the harvest of your land, thou shalt not wholly reap the corners of thy field, neither shalt thou gather the gleanings of thy harvest. And thou shalt not glean thy vineyard, neither shalt thou gather every grape of thy vineyard; thou shalt leave them for the poor and stranger: I am the LORD your God." (Leviticus 19:9-10)
In the "Biblical Perspective" for this lesson, Dr. Gordon Snider writes:

A spirit of mercy is at the core of the Judeo-Christian ethic. God is always pictured as the friend and defender of the outcast, down-trodden, and disenfranchised of society. Providing food for the poor is a part of that spirit of mercy. Never once in these verses, or the parallel texts such as Leviticus 23:22 and Deuteronomy 24:19-22, is the subject of why these people were poor considered. Instead, a social “safety net” was to be drawn under the entire society.

Discussion: Why do Christians, faced with the opportunity to help those in need, sometimes focus more on why people are poor, than how to help them?
Discussion: How can we improve our reflection of Christ's holiness in our dealings with the poor?
Source: Biblical Family Values, Adult Teacher's Insights, page 64.