He saw the Messenger of Allah ﷺ lying on his back in the mosque, with one leg resting over the other.
أنه رأي رسول الله ﷺ مستلقيا فى المسجد، واضعا إحدى رجليه على الأخرى.
Malik narrated it in "Shortening the Prayer" (93), from Ibn Shihab, from Abbad bin Tamim, from his uncle, that he saw the Messenger of Allah ﷺ and he mentioned it. Bukhari also narrated it in "Prayer" (475) and in "Clothing" (5969), and Muslim narrated it in "Clothing" (2100:75), both of them through the route of Malik, with the same wording.