The Prophet (ﷺ) saw a Bedouin making water in the mosque and told the people not to disturb him. When he finished, the Prophet (ﷺ) asked for some water and poured it over (the urine).
Sahih al-Bukhari Book 4, Hadith 85
← Previous Hadith The Prophet (ﷺ) once passed by two graves and said, "These two persons are being tortured not for a major sin (to avoid). One of them never saved himself from being soiled with his urine, while the other used to go about with calumnies (to make enmity between friends)." The Prophet (ﷺ) then took a green leaf of a date-palm tree, split it into (pieces) and fixed one on each grave. They said, "O Allah's Apostle! Why have you done so?" He replied, "I hope that their punishment might be lessened till these (the pieces of the leaf) become dry." (See the footnote of Hadith 215).

Sahih al-Bukhari Book 4, Hadith 84 Next Hadith → A Bedouin stood up and started making water in the mosque. The people caught him but the Prophet (ﷺ) ordered them to leave him and to pour a bucket or a tumbler of water over the place where he had passed the urine. The Prophet (ﷺ) then said, "You have been sent to make things easy and not to make them difficult."

Sahih al-Bukhari Book 4, Hadith 86