What exactly do doctors mean by not knocking at the door and the three commandments of doctors?

The doctor doesn't knock on the door, which means that the doctor doesn't take the initiative to visit the patient and needs the patient's invitation. There are many reasons, mainly 1 respect, 2 responsibilities and 3 people's hearts. The first two are easy to understand. The main point in people's minds is that many people will think that doctors come to the door for other purposes.

1 doctors are involuntary, divination is involuntary, 2 doctors don't knock on the door, the word doesn't spread lightly, 3 doctors don't play with diseases, and patients don't insult doctors.