Abdullah bin Umar reported,

The Prophet ﷺ saw some phlegm on the wall of the mosque facing the qiblah and became angry with the people of the mosque. He said, "Allah is in front of one of you, so when any of you is in his prayer, let him not spit," or he said, "let him not expel phlegm." Then he came down and scraped it off with his hand.Ibn Umar said, "When any of you needs to spit, let him spit to his left."

حدثنا سليمان بن حرب حدثنا حماد عن أيوب عن نافع

عن ابن عمر رضي الله عنهما

أن النبي ﷺ رأى نخامة في قبلة المسجد فتغيظ على أهل المسجد وقال إن الله قبل أحدكم فإذا كان في صلاته فلا يبزقن أو قال لا يتنخمن ثم نزل فحتها بيده وقال ابن عمر رضي الله عنهما إذا بزق أحدكم فليبزق على يساره