What is the virtue of giving free lessons in the field of medicine for the sake of Allah?

Beneficial worldly sciences, such as medicine, hold a high status in Islam. Learning and teaching them is a communal obligation (fard kifaya), and whoever undertakes them will be greatly rewarded if their intention is to serve Islam and Muslims. This knowledge falls under the category of knowledge from which one benefits even after death, and it offers great benefit to students and Muslim patients. If the intention is sincere and the reward is sought in helping Muslims to remedy deficiencies in this field, then a great reward is hoped for.