The Prophet ﷺ saw some sputum on the wall facing the Qibla of the mosque and became furious with the people of the mosque and said, "During the prayer, Allah is in front of everyone of you and so he should not spit (or said, 'He should not expectorate')." Then he got down and scratched the sputum with his hand. Ibn ʿUmar said (after narrating), "If anyone of you has to spit during the prayer, he should spit to his left."  

أَنَّ النَّبِيَّ ﷺ رَأَى نُخَامَةً فِي قِبْلَةِ الْمَسْجِدِ فَتَغَيَّظَ عَلَى أَهْلِ الْمَسْجِدِ وَقَالَ إِنَّ اللَّهَ قِبَلَ أَحَدِكُمْ فَإِذَا كَانَ فِي صَلاَتِهِ فَلاَ يَبْزُقَنَّ أَوْ قَالَ لاَ يَتَنَخَّمَنَّ ثُمَّ نَزَلَ فَحَتَّهَا بِيَدِهِ وَقَالَ ابْنُ عُمَرَ ؓ إِذَا بَزَقَ أَحَدُكُمْ فَلْيَبْزُقْ عَلَى يَسَارِهِ  

The Prophet ﷺ said, "Whenever anyone of you is in prayer, he is speaking in private to his Lord and so he should neither spit in front of him nor on his right side but to his left side under his left foot."  

عَنِ النَّبِيِّ ﷺ قَالَ إِذَا كَانَ فِي الصَّلاَةِ فَإِنَّهُ يُنَاجِي رَبَّهُ فَلاَ يَبْزُقَنَّ بَيْنَ يَدَيْهِ وَلاَ عَنْ يَمِينِهِ وَلَكِنْ عَنْ شِمَالِهِ تَحْتَ قَدَمِهِ الْيُسْرَى