Imām Bukhārī narrates: Muslim ibn Ibrāhīm narrated to us, he said: Hishām narrated to us, from Qatādah, from Anas, may Allāh be pleased with him, he narrated that the Prophet ﷺ said:
When any one of you engages in munājāt (whispered conversation) with his Lord, he should not spit towards his right, but beneath his left foot.
And Sa'īd narrated from Qatādah: A person should not spit in front of him or before him, but towards his left, or beneath his feet. And Shu'bah said: A person should not spit in front of him, nor towards his right, but towards his left, or beneath his foot. And Humaid narrated from Anas, may Allāh be pleased with him, he heard from the Prophet ﷺ that a person should not spit towards the qiblah, nor towards the right, but towards the left, or beneath the foot.
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 ".
Reference: Sahih Al Bukhari 531