It was narrated from Salim, from his father, that on one occasion the Prophet صلی اللہ علیہ وآلہ وسلم 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.” (Sahih)