Thawban reported: The Prophet, peace and blessings be upon him, said, “I certainly know people from my nation who will come on the Day of Resurrection with good deeds like the mountains of Tihamah, but Allah will scatter them like dust.” Thawban said, “O Messenger of Allah, describe them to us and tell us more, that we will not become like them.” The Prophet said, “They are your brothers and from your ehtnicity, taking up worship at night as you do, but they will be people who transgress the sacred limits of Allah when they are alone.”
Source: Sunan Ibn Mājah 4245
Grade: Sahih (authentic) according to Al-Albani
عَنْ ثَوْبَانَ عَنْ النَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ أَنَّهُ قَالَ لَأَعْلَمَنَّ أَقْوَامًا مِنْ أُمَّتِي يَأْتُونَ يَوْمَ الْقِيَامَةِ بِحَسَنَاتٍ أَمْثَالِ جِبَالِ تِهَامَةَ بِيضًا فَيَجْعَلُهَا اللَّهُ عَزَّ وَجَلَّ هَبَاءً مَنْثُورًا قَالَ ثَوْبَانُ يَا رَسُولَ اللَّهِ صِفْهُمْ لَنَا جَلِّهِمْ لَنَا أَنْ لَا نَكُونَ مِنْهُمْ وَنَحْنُ لَا نَعْلَمُ قَالَ أَمَا إِنَّهُمْ إِخْوَانُكُمْ وَمِنْ جِلْدَتِكُمْ وَيَأْخُذُونَ مِنْ اللَّيْلِ كَمَا تَأْخُذُونَ وَلَكِنَّهُمْ أَقْوَامٌ إِذَا خَلَوْا بِمَحَارِمِ اللَّهِ انْتَهَكُوهَا
4245 سنن ابن ماجه كتاب الزهد باب ذكر الذنوب
3442 المحدث الألباني خلاصة حكم المحدث صحيح في صحيح ابن ماجه