What is the ruling on one who swears excessively—and sometimes falsely—to increase his sales, and what is the ruling on his employees working for him?

A Muslim should not swear excessively, even if truthful, as Allah Almighty says: "And do not make [the name of] Allah an excuse in your oaths." If the oath is false to promote merchandise, then it is a grave sin that eradicates blessings, for the Prophet, peace and blessings be upon him, said: "The false oath promotes the merchandise but obliterates the blessing." It is obligatory to advise whoever swears falsely by clarifying the seriousness of their action, and the necessity of abstaining from swearing altogether, especially false oaths, and to explain the reward of the truthful merchant who will be "with the prophets, the truthful, and the martyrs." It is not necessary to stop working with this person; rather, doing so is a matter of piety and precaution.