Shaykh Abdul Azeez ibn Baaz rahimahullaah in his Majmoo` Fataawaa vol. 13 pg. 364 was asked the following question:
Q: If the deceased person had bequeathed for his organs to be donated, is the bequest to be carried out?
A: What is more correct is that it is not permissible to carry such a bequest out, because of that which has preceded in the answer to the first question – even if he bequeathed with such, because his body is not a possession of his.
[See a translation of the answer to the first question: https://saadburbank.com/2014/08/20/the-ruling-of-organ-transfer-after-the-passing-away-of-the-brain-dead-person/ ]
