Virtues and Merits of the Prophet (pbuh) and his Companions
حَدَّثَنَا سُلَيْمَانُ بْنُ حَرْبٍ، حَدَّثَنَا شُعْبَةُ، عَنْ قَتَادَةَ، عَنْ أَنَسٍ ـ رضى الله عنه ـ قَالَ دَعَا النَّبِيُّ صلى الله عليه وسلم الأَنْصَارَ فَقَالَ " هَلْ فِيكُمْ أَحَدٌ مِنْ غَيْرِكُمْ ". قَالُوا لاَ، إِلاَّ ابْنُ أُخْتٍ لَنَا. فَقَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " ابْنُ أُخْتِ الْقَوْمِ مِنْهُمْ ".Narrated Anas:The Prophet (ﷺ) sent for the Ansar (and when they came), he asked, 'Is there any stranger amongst you?" They said, "No except the son of our sister." Allah's Messenger (ﷺ) said, "The son of the sister of some people belongs to them
From Sahih al-Bukhari, whose reports the scholars accept as authentic.