When you reap the harvest in your field, and you forget a sheaf in the field, do not go back to get it. It is to be left for the foreign resident, the fatherless, and the widow, so that the Lord, your God, may bless you in all the work of your hands. When you knock down the fruit from your olive tree, you must not go over the branches again. What remains will be for the foreign resident, the fatherless, and the widow. When you gather the grapes of your vineyard, you must not glean what is left. What remains will be for the foreign resident, the fatherless, and the widow.This passage is particularly important in regards to hunger for several reasons. The phrase "foreign resident, the fatherless, and the widow" repeats three times to stress the importance of helping those in most need. The specific identities are relevant to the historical aspect of the Bible, as during the time, those who were a foreign resident or fatherless or a widow tended to be some of the most vulnerable in a community. So in this case, the wording of the passage can't be used literally but should instead be used figuratively to mean the most vulnerable.-Deuteronomy 24:19-21
The reason that I'm particularly drawn to this passage is because of the specific mention of gleaning. This just shows how old the practice is and also shows that there's no specific way in which to glean.
Gleaning is extremely important to at least the food pantry that I worked in and is something that isn't specific to getting left over food from farms and harvests. Most of the gleaned food that goes through the Lift Urban Portland's food pantry actually comes from stores like Trader Joes and Franz Bread and organizations like Urban Gleaners.
So next time you go grocery shopping, spend a moment considering where the unpurchased leftover food (especially produce and bread) might go at the end of the day. I personally hope that most of it ends up as donations to help stock food pantries in the area.