عَنِ ابْنِ عُمَرَ رَضِيَ اللَّهُ عَنْهُمَا عَنِ النَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَآلِهِ وَسَلَّمَ قَالَ مَنْ كَانَ حَالِفًا فَلَا يَحْلِفْ إِلَّا بِاللَّهِ عَزَّ وَجَلَّ وَكَانَتْ قُرَيْشٌ تَحْلِفُ بِآبَائِهَا فَقَالَ لَا تَحْلِفُوا بِآبَائِكُمْ
It is narrated from Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) said: Whoever wishes to swear an oath, should swear only by Allah Almighty. Since the Quraysh used to swear by their forefathers, the Prophet (peace and blessings be upon him) said to them: Do not swear by your forefathers.