ENOfficial
Narrated Ibn 'Umar (RA): Allah's Messenger (ﷺ) overtook 'Umar bin al-Khattab when he was with a party of riders of about ten and 'Umar was swearing by his father. Allah's Messenger (ﷺ) called them and said, "Verily! Allah forbids you from swearing by your fathers. Therefore, if anyone swears, he must swear by Allah or keep silent."
Source: sunnah.com
Other translations
Arabic
عَنْ اِبْنِ عُمَرَ رَضِيَ اَللَّهُ عَنْهُمَا, { عَنْ رَسُولِ اَللَّهِ - صلى الله عليه وسلم -أَنَّهُ أَدْرَكَ عُمَرَ بْنَ اَلْخَطَّابِ فِي رَكْبٍ, وَعُمَرَ يَحْلِفُ بِأَبِيهِ, فَنَادَاهُمْ رَسُولُ اَللَّهِ - صلى الله عليه وسلم -"أَلَا إِنَّ اَللَّهَ يَنْهَاكُمْ أَنْ تَحْلِفُوا بِآبَائِكُمْ, فَمَنْ كَانَ حَالِفاً فَلْيَحْلِفْ بِاَللَّهِ, أَوْ لِيَصْمُتْ" } مُتَّفَقٌ عَلَيْهِ 1 .
sunnah.com