Make a fence around your roof, so that you won’t bring bloodshed upon your house if someone falls. (Deuteronomy 22:8)

For most of history, rooftops were places for storage, drying produce, and just plain leisure. They were also hazardous. The Torah instructs us to reduce that hazard by erecting a fence or guardrail—at least 10 handbreadths tall and sturdy enough to support the weight of a grown man. Roofs that are not used (like those of most modern houses) need not be fenced.

This precept goes beyond roofs. If the Torah tells us to fence in dangerous rooftops, obviously we need to deal with other potential hazards as well. The Jewish sages provided a few examples:

  • Not just rooftops, but porches and balconies must be fenced in, and staircases equipped with sturdy railings.
  • Construction workers must cover any hole they leave behind, or surround it with a barrier. The same applies to swimming pools. Dangerous equipment and other hazardous materials must be stored away, so that they pose no danger.
  • You didn’t create your own life, so how could you be permitted to endanger it?Ideally, one shouldn’t own a dangerous dog. A dog is considered dangerous if its bark frightens people. If one must own such a dog, he must keep it chained, so that it is incapable of harming or frightening others.
  • A father is obligated to teach his children to swim.

Are You Your Own Hazard?

You didn’t create your own life, so how could you be permitted to endanger it? And so, the mitzvah of reducing hazards applies to yourself as well.

Some examples of forbidden hazards:

  • Wading through rushing waters that are higher than your waist.
  • Driving a vehicle at a dangerous speed.
  • Traversing a dangerously unstable bridge, or walking under a shaky ladder.
  • Since smoking is now recognized as a health hazard, many contemporary halachic authorities are of the opinion that it is forbidden to smoke today (and certainly in the presence of others).