Sufyan bin Sa‘id Ath-Thawri سفيان الثوري · The Book of the Masjids

"Those people, if there was a righteous man among them, when he died they built a place of worship over his grave and made those images. They will be the most evil of creation before Allah on the Day of Resurrection."

"Umar passed by Hassan bin Thabit while he was reciting poetry in the Masjid, and glared at him. He said: 'I recited poetry when there was someone better than you in the Masjid.' Then he turned to Abu Hurairah and said: 'Did you not hear the Messenger of Allah (ﷺ) when he said: "Answer back on my behalf. O Allah, help him with the Holy Spirit!'" He said: 'Yes, by Allah.'"

"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."