Silsilat al-Ahadith al-Sahihah

It is narrated from Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) that the Prophet (peace and blessings of Allah be upon him) said: "When Islam began, it was strange (unfamiliar), and soon it will become strange again, so glad tidings are for the strangers (those who adopt this religion)." It was asked: O Messenger of Allah! Who are these people? He (peace and blessings of Allah be upon him) said: "They are those who rectify (reform) the people when they become corrupt."