Can u please explain to me if and why it is permissible to kill a rodef or someone that is chasing after a narah merusah to be maanes her on shabbos?.....if yes, from where do we know it??
Clearly one may kill a Rodef on Shabbos, for Piku'ach Nefesh is Docheh Shabbos. As for a Rodef after an Ervah, ostensibly whatever is Docheh the Isur of Retzichah should also be Docheh the Isur of Shabbos as well.
However, the Mishneh l'Melech (Hilchos Shabbos 24:7) writes that it is possible that the Rishonim argue with regard to one who is Rodef after an Ervah. In addition, Rabeinu Yonah above (72b) states clearly that it may be done even on Shabbos.
For further elucidation on the topic, Rav Y. F. Perlow to Sefer ha'Mitzvos of Rav Sa'adyah Ga'on, vol. III, p. 16a.
D. Zupnik