[Machine] The Prophet ﷺ heard Umar saying, "By my father." So the Messenger of Allah ﷺ said, "Verily, Allah forbids you from swearing by your fathers. If one of you must swear, then let him swear by Allah or remain silent." Umar said, "I haven't sworn by my father after that, nor have I preferred it."
أَنَّ النَّبِيَّ ﷺ سَمِعَ عُمَرَ وَهُوَ يَقُولُ وَأَبِي فَقَالَ رَسُولُ اللهِ ﷺ إِنَّ اللهَ يَنْهَاكُمْ أَنْ تَحْلِفُوا بِآبَائِكُمْ فَإِذَا حَلَفَ أَحَدُكُمْ فَلْيَحْلِفْ بِاللهِ أَوْ لِيَصْمُتْ قَالَ عُمَرُ فَمَا حَلَفْتُ بِهَا بَعْدُ ذَاكِرًا وَلَا آثِرًا