Sahih Muslim 702
صحيح مسلم#702SahihIbn 'Umar reported:Umar said: Is one amongst us permitted to sleep in a state of impurity (i. e. after having sexual intercourse)? He (the Holy Prophet) said: Yes, after performing ablution
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Every narration in Sahih Muslim is accepted as Sahih (authentic) by the established status of the book.
In-book reference: 3:24