Musnad Ahmad 31:115

Yahya ibn Ishaq narrated to us, he said: Ibn Lahi'ah informed us, from Khalid ibn Abi 'Imran, from Abu 'Abd al-Rahman al-Hubuli, from Abu Sa'id al-Khudri, who said: The Messenger of Allah, peace and blessings of Allah be upon him, took my hand and said: "O Abu Sa'id, whoever says three things will enter Paradise." I said: "What are they, O Messenger of Allah?" He said: "Whoever is pleased with Allah as a Lord, with Islam as a religion, and with Muhammad as a Messenger." Then he said: "O Abu Sa'id, and a fourth one has a virtue like that which is between the heaven and the earth, and it is: Jihad in the way of Allah."