Final answer:
The question is unclear without additional context, and the provided excerpts do not include a specific incident involving a guide hearing a snake. Therefore, a precise answer cannot be given.
Step-by-step explanation:
The question does not provide enough context to determine the specific actions of the guide in response to the sibilant sound of a snake. The excerpts provided from various narratives show characters encountering different threatening or alarming situations, and their reactions vary widely, including cautious curiosity, flight, and seeking assistance. Without further details or a clear reference to an event in literature, it is not possible to accurately answer what the guide did when he heard the sibilant sound of a snake.