(5) باب الْحَلِفِ بِالآبَاءِ
It was narrated from Salim, from his father, that on one occasion the Prophet heard 'Umar saying:
"By my father and by my mother." He said: "Allah forbids you to swear by your forefathers." 'Umar said: "By Allah, I never swore by them again, whether saying it for myself or reporting it of others."
Reference: Sunan an-Nasa'i 3766
In-book reference: Book 35, Hadith 6
English translation: Vol. 4, Book 35, Hadith 3797