What is the ruling on one who collects donations, then mixes them with her own money, then estimates the amount and pays it out?

Question:
Our sisters from that secondary school have a somewhat lengthy case. In summary, they collect some donations from the students; some of them donate ten riyals, and some donate five riyals, as they mention. At that point, they collect these donations and give them in charity to the poor. But the issue is that one of them collects these donations and mixes them with her own money, then estimates that the donations amount to such and such. What is the guidance for these people?

Answer:
This is not permissible. It is not permissible for her to collect the donations that their owners paid for charitable causes, then mix them with her own money, and then estimate the amount of the donations and pay it out. This is because this estimation may be incorrect. It is obligatory for her to keep the donated amounts separate, because they are a trust in her hand. It is obligatory for her to keep them separate and not mix them with her own money, to avoid error and to prevent any of these donations from being included in her money, even if it is through error in estimation and mistake. This is because she is the cause of this defect by mixing these moneys. If she had isolated them and confined them to a place, that would have been safer for her, safer for the trust, and more exonerating for her conscience. Yes.