Last week’s Torah portion, Shoftim, told us not to cut down fruit trees when we are besieging a city. By Talmudic times, this injunction had been expanded into the principle of bal taschchit, do not destroy anything useful. (See my post Shoftim: Saving Trees.)
Some of the rules in this week’s Torah portion, Ki Teitzei (“When you go out”), have been similarly expanded. Here is one, nicknamed “The Forgotten Sheaf”:
If you harvest your harvest in your field, and you forget an omer in the field, you shall not turn back to take it. It shall be for the stranger, for the orphan, and for the widow, so that God, your god, will bless you in everything your hands do. (Deuteronomy/Devarium 24:19)
omer (עֹמֶר) = a dry measure, roughly 2 quarts or 2 liters, used in the Torah for both manna and cut ears of grain.
The word omer is sometimes translated as “sheaf”, but the omer of manna discussed in the book of Exodus/Shemot consists of tiny white spheres the size of coriander seed. Manna could hardly be gathered into a sheaf! Elsewhere in the Hebrew Bible, the word omer refers to grain, and can easily be translated as a quantity of grain heads. (The sheaves in Joseph’s dream in Genesis/Bereishit are called alumim (אֲלֻמִּים), an entirely different word.)
Commentators over the centuries have agreed that the purpose of the rule about the so-called “Forgotten Sheaf” could not be to provide for the poor (epitomized by three types of people unlikely to own land or to be supported by wealthy men: resident aliens, orphans, and widows). One omer of grain might feed one person for one day. Landowners and their employees would have to be extraordinarily forgetful to accidentally leave enough grain to feed all the poor in their area.

Moreover, the Torah already requires landowners to deliberately leave behind grain, grapes, and other produce for the poor to glean.
When you harvest the harvest of your land, you shall not finish harvesting to the edge of your field, nor gather up the gleanings of your harvest. And you shall not glean your vines nor gather up your fallen grapes in your vineyard; to the poor and to the stranger you shall leave them. (Leviticus/Vayikra 19:9-10)
The Torah portion for this week in Deuteronomy adds orchards to the fields and vineyards.
When you beat out your olive tree, you shall not strip the branches behind you; they shall be for the stranger, for the orphan, and for the widow. (Deuteronomy 24:20)
If landowners are already required to leave food in their fields, vineyards, and orchards for the poor to glean, why does the Torah tell them not to go back and gather an omer they forgot about?
The 13th-century book Sefer Ha-Chinukh answers that the purpose of this commandment is to help people develop the habit of generosity. Even if you are giving to the poor as required by gleaning laws, tithes, or taxes, as you work to increase your own wealth you must still cultivate the belief that sharing wealth is more important than maximizing your own profit.
Philo of Alexandria’s commentary, written in the first century C.E., criticizes people who devote themselves exclusively to increasing their own wealth, and never notice that their gains would be impossible without the natural world God gives us. (I would add that the gains of the money-hungry also require the labor of other people.) And in the 19th century, Rabbi Samson Raphael Hirsch wrote that the commandment not to go back for the forgotten omer is intended to clear possessiveness and greed from your thoughts.
Besides breaking the habits of possessiveness and greed, leaving the forgotten omer behind might also help someone to overcome the habits of worrying about being cheated, or thinking of everything in terms of private property.
What if a farmer left grain in the field, and nobody came by to pick it up? Would this violate the principle of bal tashchit, “do not waste”?
This was not an issue in ancient Israel, where there were always people without land of their own who gleaned to feed themselves.
Gleaning projects are being revived today in the United States, collecting food that would otherwise be wasted. But we can also update the principle of the forgotten omer. What if you are fumbling with your purse or billfold, and you accidentally drop money on the sidewalk? If you leave it behind, the money will not go to waste; someone will pick it up. What if you forget to collect your change at the counter, or discover you left too large a tip? Going back for your money would shrink your soul. Leaving it for someone else gives you practice in keeping your priorities straight.
When you have forgotten to do a good deed, go back. But when you have forgotten to be selfish, go on, and be grateful for your forgetfulness.