Leviticus 19:10 "And you shall not glean your vineyard"

This Mitzvah of "Tzedakah" applies also to vineyards (not just fields - see above).

While picking the fruit, we must look out for those clusters that do not have the grapes attached to a central stem. We should also notice those clusters that do not have grapes lying on one another.

These bundles are called "Ollelot".

It is forbidden to pick Ollelot. They must be left for the needy people who may come and collect them.