Pakiṇṇaka 7

The Buddha was staying in Sāvatthī. At that time, women from the Sakyan, Mallan, and Licchavi clans, as well as from aristocratic families went forth with servants. The servants were attractive, so they made them associate with men from outside, to make a living. Lay people blamed them: “These aren’t renunciates, they’re just prostitutes.” The bhikkhunīs for this reason went and informed the World-honored One. … They answered: “We really did this.” The Buddha said: “Why did you keep prostitutes to make a living? From now on, it’s no longer allowed to keep prostitutes for a living. If a bhikkhunī keeps one, she breaks a minor vinaya rule.” This is called the rule on prostitutes.