He reported from his father, who reported from his grandfather, that he heard the Prophet ﷺ say regarding the verse "You are the best nation brought forth for mankind" [Al Imran 3:110], "You complete seventy nations. You are the best of them and the most honored before Allah."
عن أبيه، عن جده أنه سمع النبي ﷺ يقول في قوله تعالى: {كنتم خير أمة أخرجت للناس} قال: أنتم تتمون سبعين أمة، أنتم خيرها، وأكرمها على الله.
Tirmidhi (3001) and Ibn Majah (4287, 4288) both narrated it through various routes from Bahz bin Hakeem, from his father, from his grandfather, who said, then he mentioned it. Its isnad is hasan because of Bahz bin Hakeem and his father, for both of them are hasan narrators of hadith.