Is it permissible for a Muslim to stay in his bedroom and lock the door with a key, for the purpose of resting and sleeping, while a maid is present in the house, knowing that he does not feel safe from temptation?

The seclusion of a man with a non-mahram (definition) woman is forbidden, based on the saying of the Messenger of Allah (peace and blessings be upon him): "No man is to be alone with a woman unless a mahram is with her." Therefore, it is not permissible to stay with a maid in a single closed house, even if each of them is in a separate room. The criterion for seclusion is an gathering where suspicion is not ordinarily dispelled.