Q. An employee we hired a couple weeks ago through a temporary agency (he is on their
A. It depends. While he is technically not your employee, your company could be liable in a claim of discrimination under a joint-employer theory. To trigger the religious accommodation requirements of Title VII, an employee must notify the employer of a conflict between a religious belief and an employment requirement.
Courts have differed on when this notice must be given. In general, however, a worker should give notice as soon as a conflict becomes apparent. Here, it appears that he may have worked a Friday or two before notifying you of his need. Assuming that his notice was proper, you have a duty to accommodate his religious needs unless his request would impose an undue hardship on the company. Anything more than a de minimus cost is considered an undue hardship, but courts differ on how much that is.
Make an honest evaluation of your needs and the financial hardship presented by the employee's request. Would you have to pay someone else overtime? Would you have to train another temp to work on Fridays? How crucial is it that workers be able to work all their scheduled days? Your question implies that he was hired on a short-term basis, which suggests that you have a pressing short-term need.
Bottom line: It may not be worth the legal headache to challenge this worker. Although your company did everything it could to document its scheduling needs to protect itself, sometimes it's too risky to test the adequacy of the documentation. Having said that, you are in a better legal position by having the documentation.