ABLUTION SECTION · 16 – Prohibition of Urinating While Standing
From Abdullah ibn Sirjis (may Allah be pleased with him):
The Messenger of Allah (peace and blessings upon him) forbade relieving oneself in holes. It was said to Katada (may Allah be pleased with him), "Why is urinating in holes disliked?" Katada replied, “It is said that they are dwellings of jinn.” [50]
EXPLANATION
*Guhr*: This means holes. It refers to things like holes in walls, hollows in trees, and small insect holes found in fields. The prohibition against urinating in such holes is due to the fact that these holes are said to be the dwellings of jinn and places where harmful insects reside. To prevent any harm from them, one is forbidden from urinating in them.

