Answer:
   
   Yes, you can. Putting out a fire on Shabbos is just one example of a
   more general rule. With rare exception, saving a life takes precedence
   over any prohibition. Among the exceptions: murder, idolatry, certain
   sexual sins, and war in certain cases. In other words, if given the
   choice between murdering another or getting killed, one must choose to
   get killed.
   
   In addition, one is permitted, but not obligated, to risk one's life
   to perform any other observance that was banned by Antisemites for the
   purpose of suppressing Judaism. The textual origin for the general
   rule is at Deut 4:5: "and you shall guard well your lives." In context
   it means something totally different, but that's where the derash
   begins. Since allowing a fire to spread to the rest of the house is a
   major threat to both the people in the house as well as people in
   neighboring houses, one is OBLIGATED to put the fire out on Shabbat.

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