Musannaf Ibn Abi Shayba 23:6

Ghundar narrated to us, from Shu'bah, from al-Hakam, who said: I heard 'Urwah ibn al-Nazzal narrating from Mu'adh ibn Jabal, who said: We arrived with the Messenger of Allah (may Allah bless him and grant him peace) from the expedition of Tabuk. When I saw him alone, I said: "O Messenger of Allah, inform me of a deed that will cause me to enter Paradise." He said: "You have asked about something great, yet it is easy for whoever Allah makes it easy for. You establish the prescribed prayer, you give the obligatory zakat, and you meet Allah while not associating anything with Him." "Shall I not guide you to the head of the matter, its pillar, and the peak of its hump? It is Jihad in the way of Allah."