"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."
مَرَّ رَجُلٌ عَلَى النَّبِيِّ ﷺ وَهُوَ يَبُولُ فَسَلَّمَ عَلَيْهِ فَلَمْ يَرُدَّ عَلَيْهِ فَلَمَّا فَرَغَ ضَرَبَ بِكَفَّيْهِ الأَرْضَ فَتَيَمَّمَ ثُمَّ رَدَّ عَلَيْهِ السَّلاَمَ