Beraisa: I might have thought that if the employer made an agreement with a shopkeeper or a moneychanger that when the worker needs food or money, they will give him and the employer will pay them back, that the employer transgresses...He does not transgress but they do transgress (if the shopkeeper or money changer agreed to pay the worker and did not do so.)

When is this the case? When the worker asked for payment.

The Mishnah taught: If the worker asked to be paid on time (and the employer claimed that he had already paid it) the worker swears that he still needs to be paid (on time) and can then take payment.

Raish Lakish: This applies when the employer responded that he had already paid him. But if he responded that he will pay the next day and then later (after the time of payment he) said that he had already paid him, he is not believed.

R. Yosi bar Chaninah: Even on the following day, if he said that he had already paid him, he is believed.

The pasuk states (Vayikra 19, 13), "Do not cheat your fellow''; this excludes a Ger Toshav (as described earlier).