Narrated 'Ubai bin 'Umar:

Abu Musa asked permission to enter upon 'Umar, but seeing that he was busy, he went away. 'Umar then said, "Didn't I hear the voice of 'Abdullah bin Qais? Allow him to come in." He was called in and 'Umar said to him, "What made you do what you did." He replied, "We have been instructed thus by the Prophet" 'Umar said, "Bring proof (witness) for this, other wise I will do so-and-so to you." Then 'Abdullah bin Qais went to a gathering of the Ansar who then said, "None but the youngest of us will give the witness for it." So Abu Said Al-Khudri got up and said, "We used to be instructed thus (by the Prophet)." 'Umar said, "This tradition of the Prophet remained hidden from me. Business in the market kept me busy."

حَدَّثَنَا مُسَدَّدٌ، حَدَّثَنَا يَحْيَى، عَنِ ابْنِ جُرَيْجٍ، حَدَّثَنِي عَطَاءٌ، عَنْ عُبَيْدِ بْنِ عُمَيْرٍ، قَالَ اسْتَأْذَنَ أَبُو مُوسَى عَلَى عُمَرَ فَكَأَنَّهُ وَجَدَهُ مَشْغُولاً فَرَجَعَ، فَقَالَ عُمَرُ أَلَمْ أَسْمَعْ صَوْتَ عَبْدِ اللَّهِ بْنِ قَيْسٍ، ائْذَنُوا لَهُ. فَدُعِيَ لَهُ فَقَالَ مَا حَمَلَكَ عَلَى مَا صَنَعْتَ فَقَالَ إِنَّا كُنَّا نُؤْمَرُ بِهَذَا. قَالَ فَأْتِنِي عَلَى هَذَا بِبَيِّنَةٍ أَوْ لأَفْعَلَنَّ بِكَ. فَانْطَلَقَ إِلَى مَجْلِسٍ مِنَ الأَنْصَارِ فَقَالُوا لاَ يَشْهَدُ إِلاَّ أَصَاغِرُنَا. فَقَامَ أَبُو سَعِيدٍ الْخُدْرِيُّ فَقَالَ قَدْ كُنَّا نُؤْمَرُ بِهَذَا. فَقَالَ عُمَرُ خَفِيَ عَلَىَّ هَذَا مِنْ أَمْرِ النَّبِيِّ ﷺ، أَلْهَانِي الصَّفْقُ بِالأَسْوَاقِ.