The Talmud teaches that Chananyah, Mishael and Azaryah were ready to give up their lives al Kiddush Hashem, because they derived that message from the frogs that plagued Egypt. Frogs have no commandment of Kiddush Hashem, and yet they jumped into fiery furnaces; they, who are commanded in Kiddush Hashem, should certainly do so. The Sefer P’ninim MiShulchan Gavoah (p. 87, cited by R. Boruch Simon in Imrei Boruch, Shemot, p. 33) relates that the Sha’agat Aryeh questioned this deduction, noting that the frogs were commanded to do what they did, as indicated by the verse the Talmud cited (Shemot 7:28), in which G-d decreed that the frogs would “go up and come into your house, and into your bed-chamber, and upon your bed, and into the house of your servants, and upon your people, and into your ovens, and into your kneading-troughs”. The Vilna Gaon, who was seven at the time, impressed the Sha’agat Aryeh by explaining that while it was true that the frogs were commanded to occupy all those locations, any individual frog could have claimed that he was not obligated to enter an oven; he could enter a bed-chamber instead. Thus, the Talmud’s logic still applies. [This question is also posed by the Resp. Shevut Ya’akov, II, 106, and answered in the same manner in the sefer Livyat Chein; see, in greater detail, Chavatzelet HaSharon al HaTorah, Shemot, pp. 89-90.] In general, the question of whether one can volunteer to sacrifice his life for mitzvot in situations where that is not obligated is the subject of a dispute among rishonim. According to Tosafot (Avodah Zarah 27b, s.v. yachol) one is permitted to voluntarily sacrifice himself. The Rambam, however, (Hil. Yesodei haTorah 5:1) forbids this, as does the Ramban (Milchamot to Sanhedrin 18a), who considers it suicide.