He traced it back to the Prophet ﷺ, who said, "One who severs ties of kinship will not enter Paradise."
حدثنا مسدد حدثنا سفيان عن الزهري
يبلغ به النبي ﷺ قال لا يدخل الجنة قاطع رحم
Muslim narrated it in the Book of Righteousness and Kinship, chapter on maintaining family ties and the prohibition of severing them, hadith no. 2556, from the hadith of Sufyan bin Uyayna, and Bukhari narrated it in the Book of Manners, chapter on the sin of the one who severs family ties, hadith no. 5984, from the hadith of Zuhri, with the same wording.