Sunan Ibn Majah 284
سنن ابن ماجه#284SahihAbdullah bin Mas'ud said:"It was said: 'O Messenger of Allah, how will you recognize those whom you have not seen of your Ummah?' He said: 'From the blazes of their foreheads and feet, like horses with black and white traces (which make them distinct from others) which are the traces of ablution.'" (Hasan) Another chain with similar wording
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Al-AlbaniHasan Sahih
Muhammad Fouad Abd al-BaqiHasan Sahih
Shuaib Al ArnautSahih Lighairihi
Zubair Ali ZaiIsnaad Hasan
In-book reference: 1:18