Majma al-Zawaid 12193 — Islam began as something strange

Sayyiduna Sahl bin Sa'd al-Sa'idi (may Allah be pleased with him) narrates that the Prophet (peace and blessings be upon him) said: "Indeed Islam began as a stranger, and soon it will again become a stranger as it began; so glad tidings to the strangers." The people asked: "O Messenger of Allah! Who are the strangers?" The Prophet (peace and blessings be upon him) said: "Those who remain upright when (other) people become corrupt."
Al-Tabarani recorded it in all three of his books, and its narrators are the narrators of the Sahih, except Bakr bin Sulaym, and he is thiqah (trustworthy).