Step 1: Understanding the Question:
The question asks for the specific action Amar Singh took to save the other man's life. "His life" refers to Narshahwaj Khan's life.
Step 2: Locating the Information in the Passage:
The passage describes the situation clearly: "He saw a desperate man dying out of thirst. Amar Singh gave him water to drink."
The following sentences confirm this saved him: "The man was now relaxed. He had got new life."
Step 3: Final Answer:
The passage states that Amar Singh found a man dying of thirst and saved him by giving him water to drink.