Silsilat al-Ahadith al-Sahihah

It is narrated from Sayyiduna Thawban (may Allah be pleased with him) that the Noble Prophet (peace and blessings be upon him) said: "I know people from my Ummah who will come on the Day of Resurrection with good deeds like the mountains of Tihamah, but Allah Almighty will make their good deeds like scattered dust in the air (insignificant)." Thawban said: O Messenger of Allah! Describe the characteristics of these people, explain them a little, lest we unknowingly become one of them. The Prophet (peace and blessings be upon him) said: "Listen! They will be your brothers, from your own lineage, and they will worship at night as you do, (but their flaw will be) that when alone, they will commit acts forbidden by Allah Almighty."