Pikuakh nefesh, save a life, is the principle of Jewish law that holds the preservation of human life above nearly every other mitzvah. It is for that reason an extremely important part of the halakha for Jews.
The principle that human life is sacred goes all the way back to God’s Creation of the earth. It comes originally from God‘s having made us in his image and likeness Gen 1:26–27. God is sacred, therefore his image and likeness are sacred.
Most of our translations make the “blood” singular, “the voice of your brother’s blood.” But the original Hebrew doesn’t say dam, blood. It says “demei, bloods.”
Mishna Sanhedrin 4.5 and Mishna Sanhedrin 37a both refer to this Hebrew word demei, bloods, referring to Abel’s blood and the bloods of all who would have been his sons and daughters until the end of time!
Mishna Sanhedrin explains God‘s use of demei: “Whoever preserves one life, it is accounted to him by Scripture as if he had preserved a whole world,” but whoever destroys one life, it is accounted to him by Scripture as if he had destroyed a whole world.”
In the life of Israel, in the life of the new Israel, pikuakh nefesh supersedes virtually every other mitzvah. Rabbi Yeshua confirmed it. “I came that they may have life, and have it abundantly” Jn 10:10.