It is narrated from Sayyiduna Samurah bin Jundub (may Allah be pleased with him); he said: The Messenger of Allah (peace and blessings be upon him) used to say to us: "Whoever among you is killed in the path of Allah, being patient and advancing forward, is in Paradise."
Hadith Referenceالمعجم الكبير للطبراني / باب السين / 7070