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.”

Volume 3, Book 34, Number 277:
Narrated ‘Ubai bin ‘Umar:
Abu Musa asked Umar to admit him but he was not admitted as ‘Umar was busy, so Abu Musa
went back. When ‘Umar finished his job he said, “Didn’t I hear the voice of ‘Abdullah bin Qais? Let
him come in.” ‘Umar was told that he had left. So, he sent for him and on his arrival, he (Abu Musa)
said, “We were ordered to do so (i.e. to leave if not admitted after asking permission thrice). ‘Umar
told him, “Bring witness in proof of your statement.” Abu Musa went to the Ansar’s meeting places
and asked them. They said, “None amongst us will give this witness except the youngest of us, Abu
Said Al-Khudri. Abu Musa then took Abu Said Al-Khudri (to ‘Umar) and ‘Umar said, surprisingly,
“Has this order of Allah’s Apostle been hidden from me?” (Then he added), “I used to be busy trading
in markets.”
Volume 3 – 468 / 1700
SAHIH BUKHARI VOLUME 3 > BOOK 34: SALES AND TRADE