"The Messenger of Allah (ﷺ) said: 'None of you should perform Ghusl in standing water when he is Junub.'"
Sunan an-Nasa'i Book 1, Hadith 221
← Previous Hadith "O Messenger of Allah, I do not become pure, so should I stop praying?" He said: "No, that is a vein." Khalid said, in what I read from him, "And it is not menstruation, so when your period comes, stop praying, and when it goes, wash the blood from yourself and pray." Meaning, before Hisham, from whom he narrates it.

Sunan an-Nasa'i Book 1, Hadith 220 Next Hadith → "None of you should urinate into still water and then perform Ghusl from it."

Sunan an-Nasa'i Book 1, Hadith 222