Sunan Abi Dawud 214
سنن أبي داود#214SahihUbayy b. Ka’b reported :The Messenger of Allah (May peace be upon him) made a concession in the early days of Islam on account of the paucity of clothes that one should not take a bath if one has sexual intercourse (and has no seminal emission). But later on her commanded to take a bath in such a case and prohibited its omission
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Al-AlbaniSahih
Muhammad Muhyi Al-Din Abdul HamidSahih
Shuaib Al ArnautSahih
Zubair Ali ZaiSahih
In-book reference: 1:214