Is the opinion of Umar contrary to the explicit Sunnah authoritative?
Chapter on the Option of the Two Parties in Sale
Al-Mughni
Book of Sales
Primary text
The opinion of Umar cannot be used as evidence to contradict the explicit statement of the Prophet, peace be upon him. If the Prophet's saying reached Umar, he would revert from his own opinion. Moreover, the opinion of a single companion is not binding when contradicted by other companions, as his son, Abu Barzah, and others held a differing view on this matter.