The Messenger of Allah ﷺ proceeded from Arafat with tranquility upon him, and he commanded the people to maintain tranquility.
حدثنا وكيع عن ابن ذر عن مجاهد
أفاض رسول الله ﷺ وعليه السكينة وأمرهم بالسكينة
Its isnad is sahih. Ibn Dharr is Umar, mentioned shortly before. The hadith has already appeared at 21653.