Prohibition of making an oath by other than Allah
حَدَّثَنَا مُحَمَّدُ بْنُ أَبِي عُمَرَ الْعَدَنِيُّ، حَدَّثَنَا سُفْيَانُ بْنُ عُيَيْنَةَ، عَنِ الزُّهْرِيِّ، عَنْ سَالِمِ بْنِ عَبْدِ اللَّهِ بْنِ عُمَرَ، عَنْ أَبِيهِ، عَنْ عُمَرَ بْنِ الْخَطَّابِ، أَنَّ رَسُولَ اللَّهِ ـ صلى الله عليه وسلم ـ سَمِعَهُ يَحْلِفُ بِأَبِيهِ فَقَالَ رَسُولُ اللَّهِ ـ صلى الله عليه وسلم ـ " إِنَّ اللَّهَ يَنْهَاكُمْ أَنْ تَحْلِفُوا بِآبَائِكُمْ " . قَالَ عُمَرُ فَمَا حَلَفْتُ بِهَا ذَاكِرًا وَلاَ آثِرًا .
It was narrated from Salim bin 'Abdullah bin 'Umar, from his father, from 'Umar, that : the Messenger of Allah (ﷺ) heard him swearing by his father. The Messenger of Allah (ﷺ) said: 'Allah forbids you from making oaths by your forefathers." 'Umar said: I never took an oath by them (i.e., my forefathers) myself nor narrating such words from anyone else.”