Sunan an-Nasa'i 406
سنن النسائي#406SahihIt was narrated from Ya'la that the Messenger of Allah (ﷺ) saw a man performing Ghusl in an open place, so he ascended the Minbar and praised and glorified Allah, then he said:'Allah, the Mighty and Sublime, is forbearing, modest and concealing, and He loves modesty and concealment. When any one of you performs Ghusl, let him conceal himself
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Abu GhuddahSahih
Al-AlbaniSahih
Zubair Ali ZaiSahih
In-book reference: 4:11