Sunan an-Nasa'i 435
سنن النسائي#435SahihIt was narrated that Ibn 'Abbas said:"Ali, Al-Miqdad and 'Ammar were talking. 'Ali said: 'I am a man who emits a lot of Madhi but I am too shy to ask the Messenger of Allah (ﷺ) about that because of his daughter's position with me, so let one of you ask him.' He told me that one of them - but I forgot who - asked him, and the Prophet (ﷺ) said: 'That is Madhi. If any one of you notices that, let him wash it off himself and perform Wudu' as for prayer or similar to the Wudu' of prayer
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Abu GhuddahSahih Isnaad
Al-AlbaniSahih Isnaad
Zubair Ali ZaiSahih
In-book reference: 4:41