In this case, one has to negotiate with demons. And so you've got to tell the ill to do good deeds, to give money in exchange for them leaving you alone. That's a convenient way to deal with them. After the crisis of the illness passes, you can then use medicine to help the body recover, and there will be no problem.
業力是要和鬼神談判的，所以要叫生病的人做功德，要叫他們用錢來交換，這是一種方便法門，等病危的情況過去了，再用人間的醫院來復健，這樣就沒問題了。