Musnad Ahmad 462:29

Hammad ibn Khalid narrated to us, he said: Mu'awiyah ibn Salih narrated to us, from Rashid ibn Sa'd, from al-Miqdam ibn Ma'di Karib al-Kindi, from the Prophet, may Allah bless him and grant him peace, that he said: "Whoever leaves behind wealth, it is for his heirs. And whoever leaves behind a debt or dependents, then it is to me, and I am the guardian of the one who has no guardian; I release him from his burden and I inherit his wealth. And the maternal uncle is the guardian of the one who has no guardian; he releases him from his burden and inherits his wealth."