We were with Umar when a man came to him and said, "Commander of the Believers, sometimes we go a month or two without finding water."Umar replied, "As for me, if I do not find water, I will not pray until I find it."Ammar bin Yasir said, "Do you remember, Commander of the Believers, when we were at such-and-such a place tending camels, and you know that we became ritually impure?"Umar said, "Yes."Ammar continued, "As for me, I rolled in the dust. Then we came to the Prophet ﷺ, and he laughed and said, 'The earth would have been enough for you.' He struck his palms on the ground, then blew into them, and wiped his face and part of his forearms."Umar said, "Fear Allah, Ammar."Ammar replied, "Commander of the Believers, if you wish, I will not mention it."Umar said, "Rather, we leave that to you, as you have taken it upon yourself."
أخبرنا محمد بن بشار قال حدثنا عبد الرحمن قال حدثنا سفيان عن سلمة عن أبي مالك وعن عبد الله بن عبد الرحمن بن أبزى
كنا عند عمر فأتاه رجل فقال يا أمير المؤمنين ربما نمكث الشهر والشهرين ولا نجد الماء فقال عمر أما أنا فإذا لم أجد الماء لم أكن لأصلي حتى أجد الماء فقال عمار بن ياسر أتذكر يا أمير المؤمنين حيث كنت بمكان كذا وكذا ونحن نرعى الإبل فتعلم أنا أجنبنا قال نعم أما أنا فتمرغت في التراب فأتينا النبي ﷺ فضحك فقال إن كان الصعيد لكافيك وضرب بكفيه إلى الأرض ثم نفخ فيهما ثم مسح وجهه وبعض ذراعيه فقال اتق الله يا عمار فقال يا أمير المؤمنين إن شئت لم أذكره قال ولكن نوليك من ذلك ما توليت
[Sahih], previously mentioned, hadith no. 313, and it is also in Sunan al-Kubra, hadith no. 302. "Part of his forearms" means his hands, as stated explicitly in the other chains of transmission. See the following hadith.