A hadith like this has been narrated by Abu Yahya al-A'raj with the same chain of transmitters.
Sahih Muslim Book 6, Hadith 146
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It was narrated to me that the Messenger of Allah (ﷺ) had said: The prayer observed by a person sitting is half of the prayer. I came to him (ﷺ) and found him praying in a sitting position. I placed my hand on his head. He said: O 'Abdullah b. 'Amr, what is the matter with you? I said: Messenger of Allah, it has been narrated to me that you said: The prayer of a man in a sitting position is half of the prayer, whereas you are observing prayer sitting. He (the Holy Prophet) said: Yes, it is so, but I am not like anyone amongst you.
Sahih Muslim Book 6, Hadith 145 Next Hadith → 'A'isha reported that the Messenger of Allah (ﷺ) used to pray eleven rak'ahs at night, observing the Witr with a single rak'ah, and when he had finished them, he lay down on his right side, till the Mu'adhdhin came to him and he (the Holy Prophet) then observed two short rak'ahs (of Sunan of the dawn prayer).
Sahih Muslim Book 6, Hadith 147
Sahih Muslim Book 6, Hadith 145 Next Hadith → 'A'isha reported that the Messenger of Allah (ﷺ) used to pray eleven rak'ahs at night, observing the Witr with a single rak'ah, and when he had finished them, he lay down on his right side, till the Mu'adhdhin came to him and he (the Holy Prophet) then observed two short rak'ahs (of Sunan of the dawn prayer).
Sahih Muslim Book 6, Hadith 147