Volume 9, Book 92, Number 451:
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 young –
est of us will give the witness for it.” So Abu Said Al-Khudri got up and said, “We used to be instruc –
ted thus (by the Prophet).” ‘Umar said, “This tradition of the Prophet remained hidden from me. Busi –
ness in the market kept me busy.”