Good Manners and Form (Al-Adab)
Ṣaḥīḥ al-Bukhārī 6108
أَلاَ إِنَّ اللَّهَ يَنْهَاكُمْ أَنْ تَحْلِفُوا بِآبَائِكُمْ، فَمَنْ كَانَ حَالِفًا فَلْيَحْلِفْ بِاللَّهِ، وَإِلاَّ فَلْيَصْمُتْ
alā inna-Llāh yanhākum an taḥlifūā bibāʾikum, faman kāna ḥālifan falyaḥlif billāh, wa-ā falyaṣmut
Transliteration generated from the Arabic vowel marks
The full narration
Narrated Ibn `Umar:that he found `Umar bin Al-Khattab in a group of people and he was swearing by his father. So Allah's Messenger (ﷺ) called them, saying, "Verily! Allah forbids you to swear by your fathers. If one has to take an oath, he should swear by Allah or otherwise keep quiet
Source
Ṣaḥīḥ al-Bukhārī · 6108
Ṣaḥīḥ