Sunan Abi Dawud 479
سنن أبي داود#479SahihIbn ‘Umar reported:One day while the Messenger of Allah(ﷺ)was giving sermon he suddenly saw phlegm on the wall towards the qiblah(the direction to which Muslims turn in prayer) of the mosque. So he became angry at people. He then scraped it and sent for saffron and stained with it. He then said: When any one of you prays, Allah, the Exalted, faces him: he, therefore, should not spit before him
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Al-AlbaniSahih
Muhammad Muhyi Al-Din Abdul HamidSahih
Zubair Ali ZaiSahih Bukhari (1213) Sahih Muslim (547)
In-book reference: 2:89