Short Answer
It is disliked to stand and urinate unless you have some excuse like an injury. It is forbidden to leave urine on the seat or to not clean yourself afterwards. It is also disliked to not seclude yourself when urinating as is done in most public urinals.
What the Qur’an and Sunnah Say
‘Ā’ishah said, “Don’t believe anyone that tells you the Prophet used to stand while urinating. He always used to sit down.” (Nasā’ī #29, Ibn Mājah #303, Aḥmad #23894)
The Prophet said, “Allah detests it when two people relieve themselves uncovered and have a conversation.” (Abū Dāwūd #15, Ahmad #10884)
Al-Mughīrah ibn Shu’bah said, “I was travelling with the Prophet. When he needed to relieve himself, he went far away from me.” (Tirmidhī #20)
The Prophet said, “When you go to the restroom, take three stones with you to clean yourself. That will suffice.” (Abū Dāwūd #36)
Salman al-Fārisī was told, “Your Prophet has taught you everything, even how to use the bathroom.” He responded, “That’s right. He told us not to…use our right hand when cleaning and to not use less than three stones to clean ourselves after we finish.” (Tirmidhī #16)
‘Ā’ishah, the Prophet’s wife, said to a group of women, “Tell your husbands to clean themselves with water because I am embarrassed to tell them. This is what the Prophet used to do regularly.” (Tirmidhī #19)
The Prophet passed by a man’s grave and told Ibn ‘Abbās that the dead man is being tortured, but not for a major sin: “He didn’t used to clean himself after urinating.” (Bukhārī #211)
The Prophet said, “Beware of the cursed ones.” Some people asked, “Who are the cursed ones?” He replied, “People who relieve themselves in public pathways or in shaded areas.” (Muslim 269)
Hudhayfah said, “The Prophet [while traveling] approached a garbage dump and stood while urinating. Then, he called me to bring some water for him, so I did, and he performed wuḍū’.” (Bukhārī #217)
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Shaykh Mustafa Umar