Is it permissible to keep the bones of the deceased (or a part thereof) for study purposes, and what should be done with them after the study is completed?

It is permissible to keep parts of the deceased for the purpose mentioned in the question. After their use, if the deceased was a non-Muslim, then the parts are not to be washed or prayed over; they are only to be buried. However, if the deceased was a Muslim, scholars have differed. Abu Hanifa and Malik held that parts of the deceased are not to be washed, shrouded, or prayed over, unless they constitute the majority of the body; rather, they are only to be buried. Conversely, Shafi'i and Ahmad held that they are to be washed, shrouded, prayed over, and buried, and this is the more preponderant view. It must be noted that it is not permissible to exhume graves and take bones of the dead for training purposes or for sale, nor is it permissible to purchase them, as that involves sin. The fundamental principle is that it is not permissible to touch any parts of the deceased except out of necessity, as determined by legitimate religious bodies and medical institutions. These parts must be preserved and not desecrated.