The Book of Mosques and Places of Prayer
Ṣaḥīḥ Muslim 1228
رَبِّهِ فَيَتَنَخَّعُ أَمَامَهُ أَيُحِبُّ أَحَدُكُمْ أَنْ يُسْتَقْبَلَ فَيُتَنَخَّعَ فِي وَجْهِهِ فَإِذَا تَنَخَّعَ أَحَدُكُمْ فَلْيَتَنَخَّعْ عَنْ يَسَارِهِ تَحْتَ قَدَمِهِ فَإِنْ لَمْ يَجِدْ فَلْيَقُلْ هَكَذَا
rabbihi fayatanakhaʿu amāmah ayuḥibbu aḥadukum an yustaqbala fayutanakhaʿa fī wajhihi fa-idhā tanakhaʿa aḥadukum falyatanakhaʿ ʿan yasārihi taḥta qadamihi fa-in lam yajid falyaqul hakadhā
Transliteration generated from the Arabic vowel marks
The full narration
Abu Huraira reported that the Messenger of Allah (ﷺ) saw some sputum in the direction of the Qibla of the mosque. He turned towards people and said:How Is it that someone amongst you stands before his Lord and then spits out in front of Him? Does any one of you like that he should be made to stand in front of someone and then spit at his face? So when any one of you spits, he must spit on his left side under his foot. But if he does not find (space to spit) he should do like this. Qasim (one of the narrators) spat in his cloth and then folded it and rubbed it
Source
Ṣaḥīḥ Muslim · 1228
- Agreed upon as authentic (al-Bukhārī / Muslim)