Sahih Muslim , Book 5, Hadith 68 (In-Book) ⓘ

Anas b. Malik reported: The Messenger of Allah said: When any one of you is engaged in prayer, he is holding intimate conversation with his Lord, so none of you must spit in front of him, or towards his right side, but towards his left side under his foot.

حَدَّثَنَا مُحَمَّدُ بْنُ الْمُثَنَّى، وَابْنُ، بَشَّارٍ قَالَ ابْنُ الْمُثَنَّى حَدَّثَنَا مُحَمَّدُ بْنُ جَعْفَرٍ، حَدَّثَنَا شُعْبَةُ، قَالَ سَمِعْتُ قَتَادَةَ، يُحَدِّثُ عَنْ أَنَسِ بْنِ مَالِكٍ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏ "‏ إِذَا كَانَ أَحَدُكُمْ فِي الصَّلاَةِ فَإِنَّهُ يُنَاجِي رَبَّهُ فَلاَ يَبْزُقَنَّ بَيْنَ يَدَيْهِ وَلاَ عَنْ يَمِينِهِ وَلَكِنْ عَنْ شِمَالِهِ تَحْتَ قَدَمِهِ ‏" ‏ ‏.‏