LEV487 When we see that someone's life is in danger, we are forbidden to stand idly by if we are able to save him (Chinuch 237). We are obligated to trouble ourselves with a lost ox or sheep; all them more so, we must aid their owners (Shaarey Tshuvah 3:71). Below are the basic laws of this commandment: 1) If you see that someone's life is endangered (for example, if you see someone drowning or being attacked by robbers), you are obligated to save him. If you are unable to rescue him yourself, you must hire someone to save him (for example, call the police). Failure to save someone is a violation of a Torah prohibition. (Choshen Mishpot 426:1). 2) There is an opinion (Yerushalmi cited by Bais Yosef, Choshen Mishpot 426:2) that one must be prepared to risk a possible threat to one's life in order to save someone whose life is definitely in danger. The rescuer takes only a doubtful risk while the other person faces a certain danger and saving one soul is equivalent to save an entire world. But the Shulchan Aruch, Rambam, Tur, RIF, and ROSH do not cite this opinion as law (SMA, Choshen Mishpat 426:1). The Chofetz Chayim writes that a person is not obligated to jeopardize his own life to save someone else. But he must weigh the matter carefully before he decides that his own life will be jeopardized by his action (Mishnah Brurah 329:19). The Aruch Hashulchan (Orach Chayim 329) adds that in such matters everything is dependent upon the particular circumstances. 3) If you overhear someone's plans to harm another person, you are obligated to inform the intended victim. When you are able to convince the schemer not to perpetrate the crime, you are obligated to do so. (Choshen Mishpot 426:1). 4) A doctor who fails to try to heal someone or is lax in his efforts violates this prohibition. (Eved Hamelech, Vayikra, p. 92b). 5) If you are able to admonish someone and fail to do so, you violate this prohibition. We are obligated to save someone's body; all the more so are we obligated to save his soul. (Minchas Chinuch 239:4). 6) If you unnecessarily told Reuven that Shimon spoke against him or wronged him, and Reuven grew angry to the extent that Shimon's life is in danger, you have an even greater obligation than usual to remove the danger. If you are unable to do so yourself, you must ask others to help you. (Shmiras Haloshon vol. 2, ch. 17). 7) It is advisable for every city to have volunteers who are prepared to rescue others from distress. (Shaarey Tshuvah 3:71). 8) If you hear that someone is planning to do something that might endanger his life, you are obligated to try to dissuade him from carrying out the act. (Pele Yoatz, section Yoatz).