Hadithcore
Sahih al-Bukhari, 340
sahih

Narrated `Abdur Rahman bin Abza:

that while he was in the company of `Umar, `Ammar said to `Umar, "We were in a detachment and became Junub and I blew the dust off my hands (performed the rolling over the earth and prayed.)"

حَدَّثَنَا سُلَيْمَانُ بْنُ حَرْبٍ، قَالَ حَدَّثَنَا شُعْبَةُ، عَنِ الْحَكَمِ، عَنْ ذَرٍّ، عَنِ ابْنِ عَبْدِ الرَّحْمَنِ بْنِ أَبْزَى، عَنْ أَبِيهِ، أَنَّهُ شَهِدَ عُمَرَ وَقَالَ لَهُ عَمَّارٌ كُنَّا فِي سَرِيَّةٍ فَأَجْنَبْنَا، وَقَالَ تَفَلَ فِيهِمَا‏.‏

References2 variants
In-Book Reference
Book 7, Hadith 7
USC-MSA web (English) reference
Vol. 1, Book 7, Hadith 336 (deprecated numbering scheme)