Shalom, There are two opinions about how Tzlofchad died. The first opinion is by Rabbi Akiva (found in the Bavli Talmud, Tractate Shabbat, page 96b) where Rabbi Akiva says that Tzlofchad was the man who chopped wood on Shabbat (Found in Parashat 'Shlach') and that was the reason for his death, the punishment for desecrating Shabbat. The second opinion is by Rabbi Yehuda ben Betera (Same place in the Talmud) and Rabbi Yehuda says that Tzlofchad was one of the 'Ma'apilim' that died by the Kna'anim (Canaanites). After the sin of the spy's when G-od punished the Jews not to enter the land of Israel, there was a group of people that without permission still entered the land of Israel and were killed by the Kna'anim (Canaanites). This group of people were called 'Ma'apilim'. Rabbi Yehuda says Tzlofchad was one of them. Rabbi Yehuda ben Betera says that Tzlofchad actually did Teshuvah and his death was to atone for the sin of the Jews in the desert and that he died with Mesirut Nefesh (self sacrifice) by giving his life away to atone for the sins of the generation. A different opinion I have heard, is that although he did do Teshuvah before he died, G-d still chose to kill him to demonstrate to the entire generation that if someone desecrates Shabbat, the result will be death. So, although he might have given his life away, as a result many became aware to observe the Shabbat with greater fear (Yir'ah) and to not desecrate it. Wishing you great success Alon Anava