Sayyiduna Uqbah bin Amir (may Allah be pleased with him) said that the Messenger of Allah (peace and blessings be upon him) said: "Every deceased person, as soon as he dies, has a seal placed upon his deeds, except the one who dies guarding the frontier in the path of Allah; his deeds continue to grow until the Day of Resurrection."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 14919