أَخْبَرَنَا قُتَيْبَةُ، عَنْ مَالِكٍ، عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم رَأَى بُصَاقًا فِي جِدَارِ الْقِبْلَةِ فَحَكَّهُ ثُمَّ أَقْبَلَ عَلَى النَّاسِ فَقَالَ " إِذَا كَانَ أَحَدُكُمْ يُصَلِّي فَلاَ يَبْصُقَنَّ قِبَلَ وَجْهِهِ فَإِنَّ اللَّهَ عَزَّ وَجَلَّ قِبَلَ وَجْهِهِ إِذَا صَلَّى " .
It was narrated from Ibn 'Umar that the Messenger of Allah (PBUH) saw some sputum on the Qiblah wall. He scrapped it off then he turned to the people and said: "When any one of you is praying, let him not spit in front of him, for Allah is in front of him when he prays." Translation Not Available
Book Ref: Sunan An Nisai Book 8 Hadith 724
Web Ref: Sunan An Nisai Vol 1 Book 8 Hadith 725