Hadithcore
Sahih al-Bukhari, 6097
sahih

Narrated Hudhaifa:

From among the people, Ibn Um `Abd greatly resembled Allah's Messengers in solemn gate and good appearance of piety and in calmness and sobriety from the time he goes out of his house till he returns to it. But we do not know how he behaves with his family when he is alone with them.

حَدَّثَنَا إِسْحَاقُ بْنُ إِبْرَاهِيمَ، قَالَ قُلْتُ لأَبِي أُسَامَةَ حَدَّثَكُمُ الأَعْمَشُ، سَمِعْتُ شَقِيقًا، قَالَ سَمِعْتُ حُذَيْفَةَ، يَقُولُ إِنَّ أَشْبَهَ النَّاسِ دَلاًّ وَسَمْتًا وَهَدْيًا بِرَسُولِ اللَّهِ صلى الله عليه وسلم لاَبْنُ أُمِّ عَبْدٍ، مِنْ حِينَ يَخْرُجُ مِنْ بَيْتِهِ إِلَى أَنْ يَرْجِعَ إِلَيْهِ، لاَ نَدْرِي مَا يَصْنَعُ فِي أَهْلِهِ إِذَا خَلاَ‏.‏

References2 variants
In-Book Reference
Book 78, Hadith 124
USC-MSA web (English) reference
Vol. 8, Book 73, Hadith 119 (deprecated numbering scheme)