ENOfficial
He reported God’s Messenger as saying, “A sister’s son has blood- relationship to her family.” (Bukhari and Muslim.)
Source: sunnah.com
Other translations
Arabic
وَعَنْهُ قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: «ابْنُ أُخْتِ الْقَوْمِ مِنْهُم».
sunnah.com