Chapter: It is forbidden to spit on the right side while in Salat (prayers)
Narrated Abu Huraira and Abu Sa`id:Allah's Messenger (ﷺ) saw some expectoration on the wall of the mosque; he took gravel and scraped it off and said, "If anyone of you wanted to spit, he should neither spit in front of him nor on his right but could spit either on his left or under his left foot."
Reference
Sahih al-Bukhari 410, 411
In-book reference
Book 8, Hadith 61
USC-MSA web (English)
Vol. 1, Book 8, Hadith 403
Translation by Dr. M. Muhsin Khan · Language: EN
Sahih
Arabic Text
حَدَّثَنَا يَحْيَى بْنُ بُكَيْرٍ، قَالَ حَدَّثَنَا اللَّيْثُ، عَنْ عُقَيْلٍ، عَنِ ابْنِ شِهَابٍ، عَنْ حُمَيْدِ بْنِ عَبْدِ الرَّحْمَنِ، أَنَّ أَبَا هُرَيْرَةَ، وَأَبَا، سَعِيدٍ أَخْبَرَاهُ أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم رَأَى نُخَامَةً فِي حَائِطِ الْمَسْجِدِ، فَتَنَاوَلَ رَسُولُ اللَّهِ صلى الله عليه وسلم حَصَاةً فَحَتَّهَا ثُمَّ قَالَ " إِذَا تَنَخَّمَ أَحَدُكُمْ فَلاَ يَتَنَخَّمْ قِبَلَ وَجْهِهِ وَلاَ عَنْ يَمِينِهِ، وَلْيَبْصُقْ عَنْ يَسَارِهِ، أَوْ تَحْتَ قَدَمِهِ الْيُسْرَى ".