Musnad Ahmad 1012:51

Hashim ibn al-Qasim and 'Affan narrated to us, they said: Muhammad ibn Talhah narrated to us, from al-A'mash, from al-Walid ibn 'Ubadah ibn al-Samit, from his father, 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, in times of difficulty and comfort, and even when preference is given to others over us. And [we pledged] that we would uphold our tongues with justice wherever we may be, not fearing for the sake of Allah the blame of any blamer." 'Affan said: "Our tongues."