Sahih Bukhari Volume 1, Book 9, Hadith 531

حَدَّثَنَا مُسْلِمُ بْنُ إِبْرَاهِيمَ، قَالَ حَدَّثَنَا هِشَامٌ، عَنْ قَتَادَةَ، عَنْ أَنَسٍ، قَالَ قَالَ النَّبِيُّ صلى الله عليه وسلم ‏"‏ إِنَّ أَحَدَكُمْ إِذَا صَلَّى يُنَاجِي رَبَّهُ فَلاَ يَتْفِلَنَّ عَنْ يَمِينِهِ، وَلَكِنْ تَحْتَ قَدَمِهِ الْيُسْرَى ‏"‏‏.‏ وَقَالَ سَعِيدٌ عَنْ قَتَادَةَ لاَ يَتْفِلُ قُدَّامَهُ أَوْ بَيْنَ يَدَيْهِ، وَلَكِنْ عَنْ يَسَارِهِ أَوْ تَحْتَ قَدَمَيْهِ‏.‏ وَقَالَ شُعْبَةُ لاَ يَبْزُقُ بَيْنَ يَدَيْهِ وَلاَ عَنْ يَمِينِهِ، وَلَكِنْ عَنْ يَسَارِهِ أَوْ تَحْتَ قَدَمِهِ‏.‏ وَقَالَ حُمَيْدٌ عَنْ أَنَسٍ عَنِ النَّبِيِّ صلى الله عليه وسلم ‏"‏ لاَ يَبْزُقْ فِي الْقِبْلَةِ وَلاَ عَنْ يَمِينِهِ، وَلَكِنْ عَنْ يَسَارِهِ أَوْ تَحْتَ قَدَمِهِ ‏"

Narrated By Anas : The Prophet said, "Whenever anyone of you offers his prayer he is speaking in private to his Lord. So he should not spit to his right but under his left foot." Qatada said, "He should not spit in front of him but to his left or under his feet." And Shu'ba said, "He should not spit in front of him, nor to his right but to his left or under his foot." Anas said: The Prophet said, "He should neither spit in the direction of his Qibla nor to his right but to his left or under his foot."