"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 ﷺ 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.'" (Using translation from Nasāʾī 316)  

يَا أَمِيرَ الْمُؤْمِنِينَ إِنَّمَا نَمْكُثُ الشَّهْرَ وَالشَّهْرَيْنِ وَلَا نَجْدُ الْمَاءَ فَقَالَ عُمَرُ أَمَّا أَنَا فَإِذَا لَمْ أَجِدِ الْمَاءَ لَمْ أَكُنْ لَأُصَلِّي حَتَّى أَجِدَ الْمَاءَ فَقَالَ عَمَّارُ بْنُ يَاسِرٍ أَتَذْكُرُ يَا أَمِيرَ الْمُؤْمِنِينَ حَيْثُ كُنْتَ بِمَكَانِ كَذَا وَكَذَا وَنَحْنُ نَرْعَى الْإِبِلَ فَتَعْلَمُ أَنَّا أَجْنَبْنَا قَالَ نَعَمْ فَأَمَّا أَنَا فَتَمَرَّغْتُ فِي التُّرَابِ فَأَتَيْتُ النَّبِيَّ ﷺ فَضَحِكَ وَقَالَ «إِنْ كَانَ الصَّعِيدُ لَكَافِيكَ» وَضَرَبَ بِكَفَّيْهِ إِلَى الْأَرْضِ ثُمَّ نَفَخَ فِيهِمَا ثُمَّ مَسَحَ وَجْهَهُ وَبَعْضَ ذِرَاعَيْهِ قَالَ اتَّقِ اللهَ يَا عَمَّارُ فَقَالَ يَا أَمِيرَ الْمُؤْمِنِينَ إِنْ شِئْتَ لَمْ أَذْكُرْهُ قَالَ لَا وَلَكِنْ نُوَلِّيكَ مِنْ ذَلِكَ مَا تَوَلَّيْتَ  

A man came to 'Umar bin khattab and said: "I became impure following sexual emission and cannot find any water." 'Umar said to him: "Do not pray." But 'Ammar bin Yasir said: "Do you not remember, O Commander of the Believers, when you and I were on a military expedition and we became sexually impure and could not find water? As for you, you did not pray, but I rolled in the dust and then prayed. When I came to the Prophet and told him what had happened, he said: 'It would have been enough for you (to do this).' (Then demonstrating) the Prophet struck the ground with his hands, then blew on hem, and wiped his face and palms with them." (Using translation from Ibn Mājah 569)   

عَمَّارٌ بْنُ يَاسِرٍ يَا أَمِيرَ الْمُؤْمِنِينَ أَتَذْكُرُ إِذْ أَنَا وَأَنْتَ فِي سَرِيَّةٍ فَأَجْنَبْنَا فَلَمْ نَجِدْ المَاءً فَأَمَّا أَنْتَ فَلَمْ تُصَلِّ وَأَمَّا أَنَا فَتَمَعَّكْتُ بالتُّرَابِ فصَلَّيْتُ فَأَتَيْنَا النبي ﷺ فذَكَرْنَا ذَلِكَ لَهُ فَقَالَ «إِنَّمَا كَانَ يَكْفِيكَ» وَضَرَبَ يَدَيْهِ إِلَى الْأَرْضِ ثُمَّ نَفَخَ فَمَسَحَ بِهِمَا وَجْهَهُ وَكَفَّيْهِ شَكَّ سَلَمَةُ فلَا أَدْرِي فِيهِ إِلَى الْمِرْفَقَيْنِ أَوْ إِلَى الْكَفَّيْنِ فقَالَ عُمَرُ نُوَلِّيكَ مِنْ ذَلِكَ مَا تَوَلَّيْتَ