The Messenger of Allah ﷺ said, "The son of a people's sister is one of them."
أخبرنا إسحق بن إبراهيم قال أنبأنا وكيع قال حدثنا شعبة عن قتادة
عن رسول الله ﷺ قال ابن أخت القوم منهم
No references are available.
Bukhari narrated it in Al-Manaqib, chapter "The nephew of a people is one of them, and the freedman of a people is one of them," Hadith 3528, and Muslim in Az-Zakah, chapter "Giving those whose hearts are to be won over for Islam, and the endurance of one whose faith is strong," Hadith 1059/105, from the hadith of Shubah through this route, and it is in Al-Kubra, Hadith 2393.