Imam Malik's Muwatta, Chapter: Jihad

Yahya related to me from Malik that Yahya ibn Said said, ''Ubada ibn al-Walid ibn Ubada ibn as-Samit informed me from his father that his grandfather (Ubada) said, 'We made a contract with the Messenger of Allah, may Allah bless him and grant him peace, to hear and obey in ease and hardship, enthusiasm and reluctance, and not to dispute with people in authority and to speak or establish the truth wherever we were without worrying about criticism.'"