Silsilat al-Ahadith al-Sahihah

It is narrated from Sayyiduna Hudhayfah bin Yaman (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "Islam will gradually fade away like the fading of embroidery on a garment, until people will not know what prayer, fasting, sacrifice, or charity are. In one night, the letters of Allah’s Book will be erased, and not a single verse will remain on the earth. The old men and old women who remain among the people will say, 'We heard our forefathers saying this word «لَا إِلَـٰهَ إِلَّا اللَّـهُ», so we also say it.'" Sila bin Zufar said to Sayyiduna Hudhayfah: "What do you mean by «لَا إِلَـٰهَ إِلَّا اللَّـهُ», when they will not know what prayer, fasting, sacrifice, or charity are?" Sayyiduna Hudhayfah turned away from him. He asked the same question three times, and each time Sayyiduna Hudhayfah avoided answering. The third time, he said: "Sila! This word will save them from Hell."