5) Chapter: Swearing By One's Forefathers
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."
5) باب الْحَلِفِ بِالآبَاءِ
أَخْبَرَنَا عُبَيْدُ اللَّهِ بْنُ سَعِيدٍ، وَقُتَيْبَةُ بْنُ سَعِيدٍ، وَاللَّفْظُ، لَهُ قَالاَ حَدَّثَنَا سُفْيَانُ، عَنِ الزُّهْرِيِّ، عَنْ سَالِمٍ، عَنْ أَبِيهِ، أَنَّهُ سَمِعَ النَّبِيُّ صلى الله عليه وسلم عُمَرَ مَرَّةً وَهُوَ يَقُولُ وَأَبِي وَأَبِي . فَقَالَ . فَوَاللَّهِ مَا حَلَفْتُ بِهَا بَعْدُ ذَاكِرًا وَلاَ آثِرًا . " إِنَّ اللَّهَ يَنْهَاكُمْ أَنْ تَحْلِفُوا بِآبَائِكُمْ "