Deuteronomy 23:26 "You shall not waive a sickle to your neighbor's standing grain"

Positive Mitzvah 201 allows a hired worker to eat from the fruit or grain that he is harvesting, but the worker must realize that he was hired to do a job.

This Negative Mitzvah forbids a worker who is hired to harvest from reaping crops for himself or eating when he is not allowed.

It also forbids a person hired to do other work besides harvesting from reaping grain for himself and eating while he is working for his employer.