While the Messenger of Allah ﷺ was sitting in the prayer row... the hadith continues.
أخبرنا علي بن حجر قال أنبأنا إسمعيل قال حدثنا يحيى بن علي بن يحيى بن خلاد بن رفاعة بن رافع الزرقي عن أبيه عن جده
أن رسول الله ﷺ بينا هو جالس في صف الصلاة الحديث
Its chain of transmission is sahih. Tirmidhi transmitted it in the Book of Prayer, Chapter on What Has Been Said Regarding the Description of Prayer, hadith no. 302, from Ali bin Hajar with this chain, and he said, "Hasan." It is also found in Al-Kubra, hadith no. 1631, in longer form. Abu Dawud transmitted it, hadith no. 861, from the narration of Ismail bin Jafar with this chain. It also has another route in Ibn Majah, hadith no. 460. Ibn Khuzayma graded the hadith sahih, hadith no. 545.