Swearing By One's Forefathers
أَخْبَرَنَا عَمْرُو بْنُ عُثْمَانَ بْنِ سَعِيدٍ، قَالَ أَنْبَأَنَا مُحَمَّدٌ، - وَهُوَ ابْنُ حَرْبٍ - عَنِ الزُّبَيْدِيِّ، عَنِ الزُّهْرِيِّ، عَنْ سَالِمٍ، عَنْ أَبِيهِ، أَنَّهُ أَخْبَرَهُ عَنْ عُمَرَ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ " إِنَّ اللَّهَ يَنْهَاكُمْ أَنْ تَحْلِفُوا بِآبَائِكُمْ " . قَالَ عُمَرُ فَوَاللَّهِ مَا حَلَفْتُ بِهَا بَعْدُ ذَاكِرًا وَلاَ آثِرًا .
It was narrated from Salim, from his father, that he told him from 'Umar: "The Messenger of Allah (ﷺ) 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."