What should be done if wetness is noticed on underwear after performing prayer?

In Islamic jurisprudence, the process of waiting for a while after urinating to ensure that any remaining drops or leakage of urine have completely ceased, and then cleaning any urine residue from the body, is called “istibra.” Istibra is especially important for men. Unless there is a valid excuse, if urine leakage occurs, the ablution (wudu) is not valid. Therefore, one should wait until the urine has fully exited the body, and for this purpose, it is recommended to move a little, walk, or cough. (Ibn Abidin, Radd al-Muhtar, 1, 344-345) The Prophet said, “Beware of urine, for most of the punishment of the grave is due to not guarding oneself from urine.” (Darqutni, as-Sunan, 1/232-233 [464-466]; see also Bukhari, Wudu’, 55 [216]; Muslim, Taharah, 111 [292]).

Accordingly, if a person who has performed istibra notices wetness on their underwear after prayer and does not know whether it is urine, they should assume it is from the clean water used during purification and should not give in to doubts. In fact, if the person is prone to doubts, it is recommended that after performing istibra, they sprinkle a small amount of clean water on their private area and underwear, and later attribute any wetness they see to this water, not urine. (Ibn Nujaym, al-Bahr, 1/252; al-Fatawa al-Hindiyya, 1/49) However, if the person knows that the wetness seen on the underwear after prayer is a drop of urine that came out before or during the prayer and remembers the moment it happened, then the prayer is considered to have been performed without ablution. This is because any discharge from the urinary tract invalidates ablution, and a prayer performed without ablution must be repeated. (Marghinani, al-Hidaya, 1/17) Additionally, if the wetness covers an area larger than the palm of the hand, the person should change the underwear or wash the soiled part.

Source: T.C. Diyanet İşleri Başkanlığı, Din İşleri Yüksek Kurulu