عَن أبي الْجُهَيْم الْأنْصَارِيّ
قَالَ: أَقْبَلَ النَّبِيُّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: مِنْ نَحْوِ بِئْرِ جَمَلٍ فَلَقِيَهُ رَجُلٌ فَسَلَّمَ عَلَيْهِ فَلَمْ يَرُدَّ عَلَيْهِ النَّبِيُّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ حَتَّى أَقْبَلَ عَلَى الْجِدَارِ فَمَسَحَ بِوَجْهِهِ وَيَدَيْهِ ثُمَّ رَدَّ عَلَيْهِ السَّلَام
Once when coming from the direction of Bir Jamal* the Prophet (sallallahu alayhi wa sallam) was met by a man who saluted him, but the Prophet (sallallahu alayhi wa sallam) did not respond to his salutation till he went towards the wall and wiped his face and his hands. Then he responded to his salutation. *A well in Medina.
Mishkat al-Masabih 495, Book 4, Purification, Hadith 231. 1 min read