Hadith 8:268
He reported God’s Messenger as saying, “He who gives refuge to a stray is astray himself as long as he does not make the matter known.” Muslim transmitted it.
وَعَنْهُ قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: «مَنْ آوَى ضَالَّةً فَهُوَ ضَالٌّ مَا لم يعرفهَا» . رَوَاهُ مُسلم
Original Reference: Mishkat al-Masabih 3034