Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) heard a man saying: Where are those who renounce this world and long for the Hereafter? Sayyiduna Abdullah (may Allah be pleased with him) said: "They were the people of al-Jabiyah, among whom five hundred Muslims pledged that they would not return until they were killed." So they shaved their heads, met the enemy, and all were killed except one who brought the news of them.
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 8552