Sunan Ibn Majah 599
سنن ابن ماجه#599Da'ifIt was narrated from 'Ali bin Abu Talib that:The Prophet said: "Whoever leaves an area the size of a hair on his body and does not cleanse it from sexual impurity, such and such will be done to him in the Fire." 'Ali said: "Because of that I am hostile towards my hair," and he used to shave his head
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Al-AlbaniDaif
Muhammad Fouad Abd al-BaqiDaif
Zubair Ali ZaiIsnaad Hasan
In-book reference: 1:333