Narrated Ibn Buraidah:
from his father: "An-Najashi gave the Prophet (ﷺ) two black plain Khuff. So he wore them, then he performed Wudu and wiped over them." (ID)
English reference (ID): Vol. 5, Book 41, Hadith 2820 (ID)
Arabic reference (ID): Book 43, Hadith 3052 (ID)