Bulugh al-Maram 127
In another narration by Hudhaifah (RAA):
"And the soil of the earth had been made for us as a means with which to purify ourselves (for prayer), when we cannot find water."
Related by Muslim.
وَفِي حَدِيثِ حُذَيْفَةَ عِنْدَ مُسْلِمٍ: { وَجُعِلَتْ تُرْبَتُهَا لَنَا طَهُورًا, إِذَا لَمْ نَجِدِ اَلْمَاءَ }   1‏ .‏‏1 ‏- صحيح.‏ رواه مسلم (522)‏، وأوله: "فضلنا على الناس بثلاث: جعلت صفوفنا كصفوف الملائكة، وجعلت.‏.‏.‏" الحديث.‏