Mishkat al-Masabih 3 Purification كتاب الطهارة 231

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

Abul Juhaim b. al-Harith b. as-Simma said that once when coming from the direction of Bi’r Jamal* the Prophet was met by a man who saluted him, but the Prophet 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. (Bukhari and Muslim.)