Musnad Ahmad 943:6

Waki’ narrated to us, al-A’mash narrated to us, from Abu Wa’il, who said: Al-Ash’ath ibn Qays entered and said: "What is Abu ‘Abd al-Rahman narrating to you?" They informed him, and al-Ash’ath said: "He spoke the truth. It was regarding me that it was revealed. There was a dispute between me and a man over some land, so I took the dispute to the Prophet, peace and blessings of Allah be upon him. He said: 'Do you have evidence?' I said: 'No.' He said: 'Then his oath.'" I said: "In that case, he will swear falsely." The Messenger of Allah, peace and blessings of Allah be upon him, said: "Whoever swears a false oath to seize the property of a Muslim man by it, while he is wicked in doing so, he will meet Allah while He is angry with him." He said: Then it was revealed: {Indeed, those who exchange the covenant of Allah and their oaths for a small price} [Al ‘Imran: 77].