it was narrated by al-Nasāʾī 1/196, and through his chain by Ibn Ḥazm in al-Muḥallā 4/261; it is also one of the versions recorded by al-Bukhārī 866 and by Abū Yaʿlā 4/1644.
Al-Ṭayālisī relates the complete wording in his Musnad 1604, and through his route Ibn Khuzaymah in his Ṣaḥīḥ 1719, explicitly naming the speaker: “al-Zuhri said ….” The same report appears in Abū Yaʿlā’s Musnad 4/1669 and al-Baghawī’s Sharḥ al-Sunnah 3/708; it is likewise the wording preserved by al-Bukhārī 837 and 849. Maʿmar inserted it from al-Zuhri in ʿAbd al-Razzāq’s al-Muṣannaf 2/245, and from him Aḥmad 6/310, as well as Abū Dāwūd in his Sunan 955—he declared it authentic—and al-Bayhaqī 2/183. This addition, however, is one of ʿAbd al-Razzāq’s slips, or those of his teacher Maʿmar.
In short, then, this extra phrase is not the statement of Umm Salamah; it goes back to al-Zuhri on the basis of what he assumed.
Moreover, the wording in the text of the book—“wa-huwa yamkuth” (“while he remains seated”)—is an inversion that crept into al-Muntaqā; the error slipped past al-Shawkānī and the present author followed him. The correct wording is “wa-yamkuthu huwa” (“and he would remain”), as in al-Bukhārī’s primary version, while Aḥmad’s abridged rendition does not contain the pronoun “huwa.”
Under the heading “The Imam or the Follower Being Elevated,” he says: “It is reported from Abū Masʿūd al-Anṣārī that the Messenger of Allah ﷺ forbade the imam to stand on something while the people were behind him, i.e., lower than he was. Related by al-Dāraquṭnī, and al-Ḥāfiẓ kept silent about it in al-Talkhīṣ.”
I say: Its chain is ḥasan, and it comes with a sound isnād in Abū Dāwūd and others; that is the report the author quotes immediately after, and it is authenticated in Ṣaḥīḥ Abī Dāwūd 610. See also al-Mishkāt 1112.
After mentioning several reports about praying on the roof of the mosque or outside it while following the imam, he says: “The default ruling is permissibility until evidence of prohibition is established.” He took this statement from al-Shawkānī.