Sayyiduna Mu'adh bin Jabal (may Allah be pleased with him) said that the Messenger of Allah (peace and blessings be upon him) led the people on a night march during the expedition of Tabuk. When morning came, he led the people in the Fajr prayer. I said: O Messenger of Allah! Tell me of a deed that will admit me into Paradise, and I will not ask you about anything besides it. He said: "Bakh bakh (excellent, excellent)! You have asked about something great, and it is easy for the one for whom Allah intends good." Then he said: "Believe in Allah and the Last Day, establish the prayer, and worship Allah alone, who has no partner, until you die in that state."
Then the Messenger of Allah (peace and blessings be upon him) said: "If you wish, O Mu'adh, I will tell you of the head of this matter, its pillar and the peak of its hump? It is jihad in the path of Allah. I have only been commanded to fight the people until they bear witness that there is no god worthy of worship except Allah, who has no partner, and that Muhammad is His servant and Messenger, and they establish the prayer and pay the zakah. When they do that, they have protected their wealth and their blood from me, except by its right, and their reckoning rests with Allah, the Mighty and Majestic."
Then the Messenger of Allah (peace and blessings be upon him) said: "By the One in whose hand my soul is, no face has grown pale, and no foot has become dusty, in any deed through which the ranks of Paradise are sought, after the obligatory prayer, like jihad in the path of Allah, the Mighty and Majestic."
Hadith Referenceالمعجم الكبير للطبراني / باب الميم / 17251