As we have seen, not only is it forbidden to eat hametz during Pesah, deriving other benefit from it is prohibited as well. In order to develop a deeper understanding of the relationship between eating and deriving benefit from forbidden foods, the Gemara compares hametz to other things forbidden by the Torah, including basar be-halav (meat and milk) and kilei ha-kerem (wheat grown in a vineyard). One point the Gemara makes very clearly is that in a case of piku’ah nefesh – of danger to human life – we dispense with all of these rules. Ravin in the name of Rabbi Yohanan taught that anything – even things usually forbidden – can be used to save someone who is in danger, with the exception of three things: Avoda Zara (idol worship), Gilui Arayot (forbidden sexual relations) and Shefikhut Damim (murder).
The Gemara presents Biblical passages as the source for this rule regarding Avoda Zara and Gilui Arayot. When it comes to Shefikhut Damim the Gemara argues that no proof-text is necessary, as it is a sevara – a logical argument – that murder cannot be permitted to save a life. To illustrate the sevara, the Gemara tells of a person who approached Rava with the following question:
“The ruler of my village came to me and said ‘kill that person, and if you do not then I will kill you.’ Can I follow his order so that I will be able to save myself?”
“Allow yourself to be killed, but you may not kill another. Who says that your blood is redder than his? Perhaps his blood is redder than yours.”
On a simple level, Rava’s argument is that we cannot tell whose life is more valuable, so we will not allow you to save your life at the expense of another.
Rabbenu Yehonatan explains Rava’s answer by arguing that really the laws of the Torah are so important that we would not allow them to be “pushed aside” even at the expense of human life. The reason the halakha permits someone to transgress a serious prohibition – like Shabbat – in order to save a life is because we weigh that single hillul Shabbat (desecration of Shabbat) against the potential Shabbatot that the person will observe in the course of his lifetime. In our case the argument is that we cannot possibly know “whose blood is redder” i.e. who will live longer and perform more mitzvot.