The Prophet ﷺ was prostrating and supplicating, "Rahman, Rahim." The polytheists said, "This man claims he calls upon one, yet he calls upon two." So Allah the Exalted revealed, "Say, call upon Allah or call upon ar-Rahman. Whichever you call, to Him belong the most beautiful names" [Isra 17:110].
كان النبي ﷺ ساجدا يدعو: يا رحمن يا رحيم فقال المشركون: هذا يزعم أنه يدعو واحدا، وهو يدعو مثنى مثنى، فأنزل الله تعالى: {قل ادعوا الله أو ادعوا الرحمن أيا ما تدعوا فله الأسماء الحسنى} الآية.
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Tabari related it in his Tafsir (15/123-124) from Qasim, who said, we were told by Husayn, who said, I was told by Muhammad bin Kathir, from Abdullah bin Waqid, from Abu Jawza, from Ibn Abbas, and he mentioned it.Its chain is hasan, because of Husayn, the author of the Tafsir, whose nickname was Sunayd, and because of his teacher Muhammad bin Kathir Masissi, for his narration is hasan except regarding Uzai and Mamar, and this narration was not related from either of them.His statement, "Do not raise your voice in your prayer, nor lower it too much, but seek a way between that" [Isra 17:110].