He said, "I saw the Messenger of Allah ﷺ raise his thumbs up to his earlobes during the prayer."
حدثنا مسدد حدثنا عبد الله بن داود عن فطر
قال رأيت رسول الله ﷺ يرفع إبهاميه في الصلاة إلى شحمة أذنيه
Reference 883, Daif. Nasai narrated it in the chapter on Opening Prayer, section on the position of the thumbs at the raising of the hands, no. 883, from the hadith of Fitr bin Khalifa, and see no. 724 for its defect.