بُلُوغُ الْمَرَامِ
Bulugh al-Maram 219
The Book of Prayer
وَعَنْ أَبِي هُرَيْرَةَ - رضى الله عنه - قَالَ : قَالَ رَسُولُ اَللَّهِ - صلى الله عليه وسلم -{ إِذَا وَطِئَ أَحَدُكُمْ اَلْأَذَى بِخُفَّيْهِ فَطَهُورُهُمَا اَلتُّرَابُ } أَخْرَجَهُ أَبُو دَاوُدَ وَصَحَّحَهُ اِبْنُ حِبَّانَ [1]
Narrated Abu Hurairah (RA): Allah's Messenger (ﷺ) said: "If one of you steps on filth with his two leather socks then the earth is their purification." [Reported by Abu Dawud, and Ibn Hibban graded it Sahih (authentic)].
Sunnah.com reference: Book 2, Hadith 83