DEUT112 This precept ["Guard your lives exceedingly carefully;" Deut. 4:15] is understood by the rabbis to apply to a wide variety of dangerous habits and behaviors involving eating, drinking, occupation, etc. Some authorities, such as Rabbi Waldenberg, a present-day [1987] halachic source of responsa on medical questions, see in it an injunction against smoking, in view of its proven relationship to cancer.