The Messenger of Allah ﷺ saw some spittle on the wall facing the qiblah, so he scraped it off. Then he turned to the people and said, "When one of you is praying, he should not spit in front of his face, for Allah is in front of his face when he prays."
أن رسول الله ﷺ رأى بصاقا في جدار القبلة فحكه، ثم أقبل على الناس فقال: إذا كان أحدكم يصلي فلا يبصق قبل وجهه، فإن الله تبارك وتعالى قبل وجهه إذا صلى.
Malik narrated it in the chapter on the qibla (4) from Nafi, from Ibn Umar, and mentioned it. Bukhari narrated it in the chapter on prayer (406), and Muslim in the chapter on masjids (547), both through the route of Malik with the same chain.Abu Dawud narrated it (479) from Sulayman bin Dawud, who said, Hammad narrated to us, who said, Ayub narrated to us, from Nafi, from Ibn Umar, who said, "While the Messenger of Allah ﷺ was delivering a sermon one day, he saw phlegm on the qibla wall of the masjid, and he became angry with the people. Then he scraped it off." He said, "And I think he said, then he called for saffron and smeared it there," and he said, "Allah is directly in front of the face of one of you when he prays, so he must not spit in front of himself."Abu Dawud said, "Ismail and Abdul-Warith narrated it from Ayub from Nafi, and Malik, Ubaydullah, and Musa bin Uqba narrated it from Nafi similarly to Hammad, except that they did not mention the saffron. Maamar narrated it from Ayub and confirmed the mention of saffron in it, and Yahya bin Salim mentioned from Ubaydullah from Nafi the word khaluq instead." End of quote.