Ibn Mājah reports in his Sunan (no. 18) with his chain of narration to Qabīsah who narrated from his father that ‘Ubādah Ibn Sāmit Al-Ansāri (may Allāh be pleased with him), the Companion of Allāh’s Messenger (صلى الله عليه وسلم) was the head of an army unit. ‘Ubādah went on a military campaign alongside Mu’āwiyah (may Allāh be pleased with him) in the land of the Byzantines.
He saw that the people were selling pieces of gold for Dīnārs (gold coins) and pieces of silver for Dirhams (silver coins). So he said: “O people! You are engaged in Ribā (interest). I heard Allāh’s Messenger (صلى الله عليه وسلم) saying: ‘Do not sell gold for gold unless it is equal measure for equal measure. There must not be any increase or delay in exchange.’”
So Mu’āwiyah said to him: “O Abul-Walīd, I do not hold there is any Ribā (interest) in this except if there is a delay in exchanging.”
So ‘Ubādah (may Allah be pleased with him) said: “I narrate to you from Allah’s Messenger (صلى الله عليه وسلم) and you narrate to me from your opinion? If Allah gets me out of here, I will never live in a land where you have authority over me.”
So when ‘Ubādah returned, he stayed in Madīnah. ‘Umar Ibn Al-Khattāb (may Allāh be pleased with him) asked him: “What has brought you here, O Abul-Walīd?” So ‘Ubādah narrated to him the story and that he would not live in a land where Mu’āwiyah had authority.
‘Umar (may Allah be pleased with him) said: “Return, O Abul-Walīd, to your land for how terrible is a land from where you and those like you are absent.” Then ‘Umar wrote to Mu’āwiyah (may Allāh be pleased with him) saying: “You have no authority over him. And make the people follow what he said for indeed that is the religion.” (Declared sahīh by Al-Albāni)
Shaikh Al-Fawzān stated: “It is not permissible to take the saying of a Faqeeh, no matter what level he has reached in Fiqh and knowledge, except if it is a clarification of the authentic evidence. However, if his view opposes the evidence, then his statement is not accepted because the saying of no person can be put alongside the saying of the Messenger (صلى الله عليه وسلم).” (See Sharh Al-Mandhūmah Al-Hā’iyyah, p. 63)