Musnad Ahmad 1012:60

Waki' narrated to us, Usamah bin Zaid narrated to us, from 'Ubadah bin al-Walid bin 'Ubadah bin as-Samit, from his grandfather 'Ubadah bin as-Samit, who said: "We pledged allegiance to the Messenger of Allah, may Allah bless him and grant him peace, to hear and obey in times of hardship and ease, and in times of willingness and unwillingness, and that we would not dispute the authority of those who hold it, and that we would speak the truth wherever we are, and that we would not fear, for the sake of Allah, the blame of any critic."