Sunan Ibn Majah #351 · The Book of Purification and its Sunnah

Sunan Ibn MajahIt was narrated that Abu Hurairah said
Sunan Ibn Majah · Book 1 · The Book of Purification and its Sunnah
Sunan Ibn Majah · كتاب 1 · كتاب الطهارة وسننها
"A man passed by the Prophet while he was urinating, and greeted him with the Salam, but he did not return the greeting. While he finished, he struck the ground with his palms and did dry ablution (Tayammum), then he returned the greeting
حَدَّثَنَا هِشَامُ بْنُ عَمَّارٍ، حَدَّثَنَا مَسْلَمَةُ بْنُ عُلَىٍّ، حَدَّثَنَا الأَوْزَاعِيُّ، عَنْ يَحْيَى بْنِ أَبِي كَثِيرٍ، عَنْ أَبِي سَلَمَةَ، عَنْ أَبِي هُرَيْرَةَ، قَالَ مَرَّ رَجُلٌ عَلَى النَّبِيِّ ـ صلى الله عليه وسلم ـ وَهُوَ يَبُولُ فَسَلَّمَ عَلَيْهِ فَلَمْ يَرُدَّ عَلَيْهِ فَلَمَّا فَرَغَ ضَرَبَ بِكَفَّيْهِ الأَرْضَ فَتَيَمَّمَ ثُمَّ رَدَّ عَلَيْهِ السَّلاَمَ ‏.‏
Reference : Sunan Ibn Majah 351In-book reference : Book 1, Hadith 85