"you are saving my life again" . why did the prisoner say this ?

give new answer in 2-3 marks in easy simple language

Dr. Sadao had already saved the life of the prisoner once, by performing a surgery on him to take out the bullet and then had nursed him too, without informing anyone, inspite of him being a citizen of his enemy country. He could have handed him over to the major but he didn't do so. Rather, out of humanity, he was helping him to run and hence was saving him once again. That is why the prisoner said so.