Deuteronomy 24:19 When thou cuttest down thine harvest in thy field, and hast forgot a sheaf in the field, thou shalt not go again to fetch it: it shall be for the stranger, for the fatherless, and for the widow: that the LORD thy God may bless thee in all the work of thine hands.
God had a tremendous way of taking care of the poor in Israel. They were to gather their own food but those who were producing were to allow there to be food available. This goes very strongly against the culture that I was raised with. The farmers were I come from would see to it that they got all the fruit and not be allowing the poor to come into their fields and glean.
For you the missionary this is a way to recognize that God understands cultural differences. One of the hardest things that you will deal with when you leave your country is adjusting to the way the people in your adopted country do things. Their ways will not be your ways. You will want to say that they are wrong. If God gives the instructions that we see in these verses and they go against our culture maybe we are wrong or at least will have to recognize that there is more than one way to do things.
Learn to adapt. Don’t be telling them that it is wrong because of your cultural preparation and perspective. You are the visitor and stranger. Learn the ways of your people.