Sahih al-Bukhari 2778
Abu 'Abdur-Rahman narrated:
When 'Uthman (ra) was circled (by the rebels), he looked upon them from above and said, "Ias you by Allah, I ask nobody but the Companions of the Prophet (ﷺ), dont you know that Allah's Messenger (ﷺ) said, 'Whoever  will (buy and) dig the well of Ruma will be granted Paradise,' and I (bought and) dug it? Don't you know that he said. 'Whoever equip the army of 'Usra (i.e., Tabuk's Ghazwa) will be granted Paradise,' and I equipped it ?" They attested whatever he said.
When 'Umar founded his endowment he said, "Its administrator can eat from it." The management of the endowment can be taken over by the founder himself or any other person, for both cases are permissible.
وَقَالَ عَبْدَانُ أَخْبَرَنِي أَبِي، عَنْ شُعْبَةَ، عَنْ أَبِي إِسْحَاقَ، عَنْ أَبِي عَبْدِ الرَّحْمَنِ، أَنَّ عُثْمَانَ ـ رضى الله عنه ـ حَيْثُ حُوصِرَ أَشْرَفَ عَلَيْهِمْ وَقَالَ أَنْشُدُكُمْ وَلاَ أَنْشُدُ إِلاَّ أَصْحَابَ النَّبِيِّ صلى الله عليه وسلم، أَلَسْتُمْ تَعْلَمُونَ أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ ‏"‏ مَنْ حَفَرَ رُومَةَ فَلَهُ الْجَنَّةُ ‏"‏‏.‏ فَحَفَرْتُهَا، أَلَسْتُمْ تَعْلَمُونَ أَنَّهُ قَالَ ‏"‏ مَنْ جَهَّزَ جَيْشَ الْعُسْرَةِ فَلَهُ الْجَنَّةُ ‏"‏‏.‏ فَجَهَّزْتُهُمْ‏.‏ قَالَ فَصَدَّقُوهُ بِمَا قَالَ‏.‏ وَقَالَ عُمَرُ فِي وَقْفِهِ لاَ جُنَاحَ عَلَى مَنْ وَلِيَهُ أَنْ يَأْكُلَ‏.‏ وَقَدْ يَلِيهِ الْوَاقِفُ وَغَيْرُهُ فَهْوَ وَاسِعٌ لِكُلٍّ‏.‏