Why does the Rambam in Hilchos G'nayvos say that there is a "license" to kill the thief breaking in, but the Gemorah, Sanhedrin 72a, indicates that it is a religious duty to kill -- As it is written in the Gemorah ad loc.: "The Torah declares: 'Im boh l'hargoch, hashkaym l'horgoh.'"
David Isaac Caplan, Delray Beach, FL 33484 USA
Sefer Ner Mitzvah to Sefer ha'Mitzvos of Rambam (Lo Sa'aseh #293) explains that since the thief is not a classic Rodef (because his main intention is to steal money), it is only a Reshus to kill him. (The Gemara's statement of "Hashkem v'Horgo" refers to a person whose main intent is to kill.)
D. Zupnik
See 73A Tos. D"H af rozteach
Tosfos there says that we do not see from the Pasuk about Machteres that it is a *Mitzvah* to kill the thief, just a Reshus, which is indeed the Halachah for which we needed a source.
However, from Tosfos it is not clear that this remains the Halachah even *after* we see from the second verse ("Ka'asher Yakum") that it is a *Mitzvah* to kill a Rotze'ach. Perhaps the second verse applies to both Machteres and a normal Rodef. From the Rambam it is clear that the distinction remains l'Halachah. (See also Margoliyos ha'Yam on that Tosfos, who cites others who discuss the difference between a thief and a normal Rodef.)
M. Kornfeld