Musnad Ahmad 8:91

'Abd al-Malik ibn 'Amr narrated to us, Kathir ibn Zayd al-Aslami narrated to us, from al-Muttalib, from 'Umar ibn Sa'd, from his father, that he said: His son 'Amir came to him and said: "O my father, do you command me to be a leader during the tribulation (fitna)?" He replied: "No, by Allah, not until I am given a sword; if I strike a believer with it, it will recoil from him, and if I strike a disbeliever with it, it will kill him. I heard the Messenger of Allah, peace and blessings of Allah be upon him, say: 'Indeed, Allah, the Almighty and Majestic, loves the wealthy, hidden, pious one.'"