Hadith 1:116
Abud Darda’ said:
While we were with God’s messenger discussing what would come to pass God’s messenger said, “When you hear that a mountain has moved from its place believe it; but when you hear that a man's nature has changed do not believe it, for he will remain true to his inborn disposition.” Ahmad transmitted it.
وَعَنْ أَبِي الدَّرْدَاءِ قَالَ بَيْنَمَا نَحْنُ عِنْدَ رَسُولِ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ نَتَذَاكَرُ مَا يَكُونُ إِذْ قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: إِذَا سَمِعْتُمْ بِجَبَلٍ زَالَ عَن مَكَانَهُ فصدقوا وَإِذَا سَمِعْتُمْ بِرَجُلٍ تَغَيَّرَ عَنْ خُلُقِهِ فَلَا تصدقوا بِهِ وَإنَّهُ يَصِيرُ إِلَى مَا جُبِلَ عَلَيْهِ ". رَوَاهُ أَحْمَدُ
Original Reference: Mishkat al-Masabih 123