Musannaf Ibn Abi Shayba 28:89

Waki’ narrated to us, he said: Sufyan and Mis’ar narrated to us, from ‘Abd al-Malik ibn ‘Umayr, from Qabisah ibn Jabir, he said: ‘Umar said: Bravery and cowardice are traits or characteristics in men. The brave man fights for the sake of one he does not care whether he returns to his family or not. And the coward flees, leaving his father and his mother.