Messenger of Allah ﷺ met ʿUmar bin Al-Khattab while the latter was going with a group of camel-riders, and he was swearing by his father. The Prophet ﷺ said, "Lo! Allah forbids you to swear by your fathers, so whoever has to take an oath, he should swear by Allah or keep quiet."
أَنَّ رَسُولَ اللَّهِ ﷺ أَدْرَكَ عُمَرَ بْنَ الْخَطَّابِ وَهْوَ يَسِيرُ فِي رَكْبٍ يَحْلِفُ بِأَبِيهِ فَقَالَ أَلاَ إِنَّ اللَّهَ يَنْهَاكُمْ أَنْ تَحْلِفُوا بِآبَائِكُمْ مَنْ كَانَ حَالِفًا فَلْيَحْلِفْ بِاللَّهِ أَوْ لِيَصْمُتْ