عَنْ سَعْدِ بْنِ عُبَيْدَةَ قَالَ كُنْتُ مَعَ ابْنِ عُمَرَ رَضِيَ اللَّهُ عَنْهُمَا فِي حَلْقَةٍ فَسَمِعَ رَجُلًا فِي حَلْقَةٍ أُخْرَى وَهُوَ يَقُولُ لَا وَأَبِي فَرَمَاهُ ابْنُ عُمَرَ رَضِيَ اللَّهُ عَنْهُمَا بِالْحَصَى وَقَالَ إِنَّهَا كَانَتْ يَمِينَ عُمَرَ رَضِيَ اللَّهُ عَنْهُ فَنَهَاهُ النَّبِيُّ صَلَّى اللَّهُ عَلَيْهِ وَآلِهِ وَسَلَّمَ عَنْهَا وَقَالَ إِنَّهَا شِرْكٌ
It is narrated from Sa'd bin Ubaidah, he says: I was in a gathering with Sayyiduna Abdullah bin Umar (may Allah be pleased with them), when he heard a man sitting in another gathering say: "No, by my father's oath," so he threw a pebble at him and said: Sayyiduna Umar (may Allah be pleased with him) used to swear in the same way, but the Noble Prophet (peace and blessings be upon him) said: This is shirk (associating partners with Allah).