Musnad Ahmad 28:126

Hassan narrated to us, Ibn Lahi'ah narrated to us, Huyayy ibn Abdullah narrated to me, that Abu Abd al-Rahman narrated to him, that Abdullah ibn Amr said: A man came to the Prophet, peace and blessings of Allah be upon him, and asked him about the best of deeds. The Messenger of Allah, peace and blessings of Allah be upon him, said: "The prayer." Then he said: "What else?" He said: "The prayer." Then he said: "What else?" He said: "The prayer," three times. He said: When he persisted, the Messenger of Allah, peace and blessings of Allah be upon him, said: "Jihad in the way of Allah." The man said: "But I have two parents." The Messenger of Allah, peace and blessings of Allah be upon him, said: "I command you to treat your parents well." He said: "By the One who sent you with the truth as a Prophet, I will surely strive (in Jihad) and I will surely leave them." The Messenger of Allah, peace and blessings of Allah be upon him, said: "You know best."