I was with Ibn Umar, and he was praying on his mount, turning this way and that. I asked him about it, and he said, "This is how I saw the Messenger of Allah ﷺ do it."
حدثنا أبو أحمد الزبيري حدثنا سفيان عن منصور
كنت مع ابن عمر فكان يصلي على راحلته هاهنا وهاهنا فقلت له فقال هكذا رأيت رسول الله ﷺ يفعل
Its isnad is sahih. Mansur is Ibn Mutamir. Abdul-Rahman bin Saad is the freedman of Abdullah bin Umar, and he is trustworthy, Nasai deemed him trustworthy, and Ibn Hibban mentioned him among the trustworthy narrators (Thiqat). The meaning of the hadith has appeared repeatedly before, the last time being at 4956. As for Abdul-Rahman bin Saad's statement "so I said to him," he means that he asked him about that, and it will come again by this same route in detail at 5047 and 5048.