The orphan's money should be protected, and it is highly desirable that the trustees invest the money for the benefit of the orphan. Allah Almighty says: (And do not come near the wealth of the orphan unless intending to enhance it until they attain maturity) Surah Al An'am 6: 152.
يجب حفظ مال اليتيم من الضياع كما يستحب الإتجار به لمصلحة اليتيم، لقوله تعالى: (وَلَا تَقْرَبُوا مَالَ الْيَتِيمِ إِلَّا بِالَّتِي هِيَ أَحْسَنُ حَتَّىٰ يَبْلُغَ أَشُدَّهُ) الأنعام 6: 152.

One must protect the orphan's money, and the orphan must be prevented from spending it, for his own interest and that of his family, until the orphan reaches the age of sound judgment.

Allah Almighty says: (Do not entrust the incapable among your dependants with your wealth which Allah has made a means of support for you but feed and clothe them from it, and speak to them kindly. Test the competence of the orphans until they reach a marriageable age. Then if you feel they are capable of sound judgment, return their wealth to them. And do not consume it wastefully and hastily before they grow up to demand it. If the guardian is well off, they should not take compensation; but if the guardian is poor, let them take a reasonable provision. When you give orphans back their property, call in witnesses. And sufficient is Allah as a vigilant Reckoner.) Surah An Nisa'a 4: 6.
تجب الوصاية على مال اليتيم، ويجب منعه في التصرف به بما يحقق المصلحة والخير له ولأهله، حتى يبلغ اليتيم سن الرشد.

قال الله تعالى: (وَلَا تُؤْتُوا السُّفَهَاءَ أَمْوَالَكُمُ الَّتِي جَعَلَ اللَّهُ لَكُمْ قِيَامًا وَارْزُقُوهُمْ فِيهَا وَاكْسُوهُمْ وَقُولُوا لَهُمْ قَوْلًا مَّعْرُوفًا * وَابْتَلُوا الْيَتَامَىٰ حَتَّىٰ إِذَا بَلَغُوا النِّكَاحَ فَإِنْ آنَسْتُم مِّنْهُمْ رُشْدًا فَادْفَعُوا إِلَيْهِمْ أَمْوَالَهُمْ ۖ وَلَا تَأْكُلُوهَا إِسْرَافًا وَبِدَارًا أَن يَكْبَرُوا ۚ وَمَن كَانَ غَنِيًّا فَلْيَسْتَعْفِفْ ۖ وَمَن كَانَ فَقِيرًا فَلْيَأْكُلْ بِالْمَعْرُوفِ ۚ فَإِذَا دَفَعْتُمْ إِلَيْهِمْ أَمْوَالَهُمْ فَأَشْهِدُوا عَلَيْهِمْ ۚ وَكَفَىٰ بِاللَّهِ حَسِيبًا) النساء 4: 6.

Caring for his interests involves shoving off anything harmful, obtaining what is good for them, and fulfilling their needs. Allah Almighty says: (And they ask you O Prophet concerning orphans. Say, Improving their condition is best. And if you partner with them, they are bonded with you in faith. And Allah knows who intends harm and who intends good.) Surah Al Baqara 2: 220.
القيام على مصالحه بدفع الشرور عنه وجلب المصالح وقضاء الحاجات. قال الله تعالى: (وَيَسْأَلُونَكَ عَنِ الْيَتَامَىٰ ۖ قُلْ إِصْلَاحٌ لَّهُمْ خَيْرٌ ۖ وَإِن تُخَالِطُوهُمْ فَإِخْوَانُكُمْ ۗ وَاللَّهُ يَعْلَمُ الْمُفْسِدَ مِنَ الْمُصْلِحِ) البقرة 2: 220.