“If any of you sneezes and praises Allah, it is incumbent upon every Muslim who hears him to invoke mercy for him.” In another wording: “to say: ‘May Allah have mercy on you.’”
Al-Bukhari recorded it in his Sahih—according to the first wording—and in al-Adab al-Mufrad—according to the other wording. It is also documented in al-Irwa (779) through several additional sources. Ibn Hibban (1/401/597) likewise declared it authentic. Al-Nasa’i related it in al-Yawm wa al-Laylah (214 and 215), and Ibn al-Sunni transmitted it from him (251).
I say: This is an explicit text clearly establishing the obligation of invoking mercy for the sneezer upon everyone who hears him praise Allah. It is therefore an individual obligation upon all. Remarkably, al-Hafiz did not discuss this issue in his commentary on this hadith in al-Fath (10/607)! *
3095—(“The form of speech he disliked most was—namely—poetry.”)
Al-Tayalisi recorded it in his Musnad (1490), and al-Bayhaqi transmitted it from him in al-Sunan (10/245): Al-Aswad ibn Shayban narrated to us: Abu Nawfal ibn Abi Aqrab narrated to us: Aisha was asked, “Was poetry recited in the presence of the Messenger of Allah, peace and blessings be upon him?” She replied … and he then cited it.
Ibn Abi Shaybah recorded it through this route in al-Musannaf (8/722/6142), as did Ahmad (6/134, 148, 188–189) through several routes from al-Aswad with the same chain. Ahmad added in one narration: “He liked concise, comprehensive supplications and would leave aside all else.”
Abu Dawud and others also transmitted it. Ibn Hibban, al-Hakim, and al-Dhahabi declared it authentic. It is documented in Sahih Abi Dawud (1332), and its chain of transmission is authentic according to Muslim’s criteria, as I explained there.
Ahmad also added: “Aisha said: ‘When the righteous are mentioned, then let Umar be mentioned!’”