Muwatta Malik, Book 36, Hadith 1446 (In-Book)

Malik related to me from Ibn Shihab from Abu Salama ibn Abd ar- Rahman ibn Awf from Jabir ibn Abdullah al-Ansari that the Messenger of Allah, may Allah bless him and grant him peace, said, "If someone is given a life pension, for him and his posterity, it belongs to the person to whom it has been given. It never reverts to the one who gave it because he gave a gift and the rules of inheritance apply to it."

حَدَّثَنِي مَالِكٌ، عَنِ ابْنِ شِهَابٍ، عَنْ أَبِي سَلَمَةَ بْنِ عَبْدِ الرَّحْمَنِ بْنِ عَوْفٍ، عَنْ جَابِرِ بْنِ عَبْدِ اللَّهِ الأَنْصَارِيِّ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ ‏ "‏ أَيُّمَا رَجُلٍ أُعْمِرَ عُمْرَى لَهُ وَلِعَقِبِهِ فَإِنَّهَا لِلَّذِي يُعْطَاهَا لاَ تَرْجِعُ إِلَى الَّذِي أَعْطَاهَا أَبَدًا ‏" ‏ ‏.‏ لأَنَّهُ أَعْطَى عَطَاءً وَقَعَتْ فِيهِ الْمَوَارِيثُ ‏.‏

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also referenced under: Book 36, Hadith 43 (USC-MSA)