Yazid bin Abi Habib narrated from Ibn Shihab, from Abu Salamah, from Jabir, that the Messenger of Allah ruled concerning 'Umra -when a man gives a gift to another man, and his descendants, but stipulates that if something happens to you and your descendants, then it will belong to me and my descendants- "It belongs to the one to whom it was given, and to his descendants." (Using translation from Nasāʾī 3749)  

أَنَّ رَسُولَ اللهِ ﷺ «قَضَى بِالْعُمْرَى أَنْ يَهَبَ الرَّجُلُ لِلرَّجُلِ وَلِعَقِبِهِ الْهِبَةَ وَيَسْتَثْنِي إِنْ حَدَثَ بِكَ حَدَثٌ وَبِعَقِبِكَ فَهُوَ إِلَيَّ وَإِلَى عَقِبِي إِنَّهَا لِمَنْ أُعْطِيَهَا وَلِعَقِبِهِ»  

[Machine] The Messenger of Allah ﷺ ruled that a man should donate to another man and his descendants, except if it happens to be your descendant, then it is for me and my descendants. Indeed, it is for whoever is given it and his descendants. Al-Uqail also narrated it in the sense of narrating from these people, while Al-Awza'i disagreed with them and narrated it from Al-Zuhri.  

أَنَّ رَسُولَ اللهِ ﷺ قَضَى بِالْعُمْرَى أَنْ يَهَبَ الرَّجُلُ لِلرَّجُلِ وَلِعَقِبِهِ وَاسْتَثْنَى إِنْ حَدَثَ بِعَقِبِكَ فَهُوَ إِلِيَّ وَإِلَى عَقِبِي إِنَّهَا لِمَنْ أُعْطِيَهَا وَلِعَقِبِهِ وَرَوَاهُ أَيْضًا عُقَيْلٌ بِمَعْنَى رِوَايَةِ هَؤُلَاءِ وَخَالَفَهُمُ الْأَوْزَاعِيُّ فَرَوَاهُ عَنِ الزُّهْرِيِّ