Umar bin Khattab wrote to Abu Ubayda that the Messenger of Allah ﷺ said, "Allah and His Messenger are the guardians of one who has no guardian, and the maternal uncle is the heir of one who has no heir."
كتب عمر بن الخطاب إلى أبي عبيدة أن رسول الله ﷺ قال: الله ورسوله مولى من لا مولى له، والخال وارث من لا وارث له.
Tirmidhi (2103) and Ibn Majah (2737) both narrated it from the hadith of Sufyan Thawri, from Abdul-Rahman bin Harith bin Ayyash bin Abu Rabia, from Hakeem bin Hakeem bin Abbad bin Hunayf, from Abu Umama, who related it. From this same route, it was also narrated by Ahmad (189), Daraqutni (4/84-85), Bayhaqi (6/214), and Ibn Jarud (964), and Ibn Hibban graded it sahih (6037). Tirmidhi said, "Hasan sahih."I say, rather it is only hasan, for Abdul-Rahman bin Harith is disputed. Abu Hatim said, a shaykh. Ibn Main said, there is no harm in him. Ajli and Ibn Hibban confirmed his reliability, and Ibn Hibban included his hadith in his Sahih. Ali bin Madini and Nasai criticized him, however his hadith is hasan.