Sunan an-Nasa'i, Volume 1, Book 1, Hadith 317 (DarusSalam)

It was narrated that 'Abddur-Rahman bin Abza said: "We were with 'Umar when a man came to him and said: 'O Commander of the Believers! sometimes we stay for a month or two without finding any water. Umar said: As if I did not find water, I would not pray until I found water.' 'Ammar bin Yasir said: 'Do you remember, O Commander of the Believer, when you were in such and such a place and we were rearing the camels, and you know that we became Junub?' He said: 'Yes.' 'As for me I rolled in the dust, then we came to the Prophet and he laughed and said: "Clean earth would have been sufficient for you." And he struck his hands on the earth then blew on them, then he wiped his face and part of his forearms. He ('Umar) said: "Fear Allah, O 'Ammar!'" He said: 'O Commander of the Believers! If you wish I will not mention it.' He said: 'No, we will let you bear the burden of what you took upon yourself.'"

أَخْبَرَنَا مُحَمَّدُ بْنُ بَشَّارٍ، قَالَ حَدَّثَنَا عَبْدُ الرَّحْمَنِ، قَالَ حَدَّثَنَا سُفْيَانُ، عَنْ سَلَمَةَ، عَنْ أَبِي مَالِكٍ، وَعَنْ عَبْدِ اللَّهِ بْنِ عَبْدِ الرَّحْمَنِ بْنِ أَبْزَى، عَنْ عَبْدِ الرَّحْمَنِ بْنِ أَبْزَى، قَالَ كُنَّا عِنْدَ عُمَرَ فَأَتَاهُ رَجُلٌ فَقَالَ يَا أَمِيرَ الْمُؤْمِنِينَ رُبَّمَا نَمْكُثُ الشَّهْرَ وَالشَّهْرَيْنِ وَلاَ نَجِدُ الْمَاءَ ‏.‏ فَقَالَ عُمَرُ أَمَّا أَنَا فَإِذَا لَمْ أَجِدِ الْمَاءَ لَمْ أَكُنْ لأُصَلِّيَ حَتَّى أَجِدَ الْمَاءَ ‏.‏ فَقَالَ عَمَّارُ بْنُ يَاسِرٍ أَتَذْكُرُ يَا أَمِيرَ الْمُؤْمِنِينَ حَيْثُ كُنْتَ بِمَكَانِ كَذَا وَكَذَا وَنَحْنُ نَرْعَى الإِبِلَ فَتَعْلَمُ أَنَّا أَجْنَبْنَا قَالَ نَعَمْ أَمَّا أَنَا فَتَمَرَّغْتُ فِي التُّرَابِ فَأَتَيْنَا النَّبِيَّ صلى الله عليه وسلم فَضَحِكَ فَقَالَ ‏ "‏ إِنْ كَانَ الصَّعِيدُ لَكَافِيكَ ‏" ‏ ‏.‏ وَضَرَبَ بِكَفَّيْهِ إِلَى الأَرْضِ ثُمَّ نَفَخَ فِيهِمَا ثُمَّ مَسَحَ وَجْهَهُ وَبَعْضَ ذِرَاعَيْهِ ‏.‏ فَقَالَ اتَّقِ اللَّهَ يَا عَمَّارُ ‏.‏ فَقَالَ يَا أَمِيرَ الْمُؤْمِنِينَ إِنْ شِئْتَ لَمْ أَذْكُرْهُ ‏.‏ قَالَ لاَ وَلَكِنْ نُوَلِّيكَ مِنْ ذَلِكَ مَا تَوَلَّيْتَ ‏.‏

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also referenced under: Book 1, Hadith 318 (In-Book)