The Messenger of Allah ﷺ heard me swearing an oath by my father and said: “Allah forbids you to swear by your fathers.” ‘Umar said: By Allah, I never swore by my father after that, whether saying it myself or narrating what someone else had said.
سَمِعَنِي رَسُولُ اللهِ ﷺ وَأَنَا أَحْلِفُ بِأَبِي فَقَالَ إِنَّ اللهَ يَنْهَاكُمْ أَنْ تَحْلِفُوا بِآبَائِكُمْ قَالَ عُمَرُ فَوَاللهِ مَا حَلَفْتُ بِهَا بَعْدُ ذَاكِرًا وَلا آثِرًا