Musnad Ahmad 28:382

'Affan and Bahz narrated to us, they said: Shu'bah narrated to us, from Habib ibn Abi Thabit, who said: I heard Abu al-'Abbas—and he was a poet—I heard 'Abdullah ibn 'Amr say: A man came to the Messenger of Allah, may Allah bless him and grant him peace, and asked his permission for Jihad. He said: "Are your parents alive?" He said: "Yes." He said: "Then in them, strive (perform Jihad)." Bahz said: Habib ibn Abi Thabit informed me, from Abu al-'Abbas, he said: I asked 'Abdullah ibn 'Amr.