I asked Ayesha, "Did the Messenger of Allah ﷺ combine surahs in a single rakah?"She replied, "Yes, from the Mufassal."
حدثنا وكيع حدثنا كهمس بن الحسن
قلت لعائشة هل كان رسول الله ﷺ يجمع بين السور في ركعة قالت المفصل
Its isnad is sahih. Ibn Khuzayma reported it (1/271, no. 539), and Hakim graded it sahih (1/265), and Dhahabi agreed with him.