Bamidbar Rabbah c21 – A purposely mistranslated text.
The Quote
Every Jew who spills the blood fo the non-Jew is doing the same as making a sacrifice to God
— Bamidbar Rabbah c21
The Reality
For starters, the citation is garbled. There is no “c21.” The correct citation is Bamidbar Rabbah 21.
In addition, Bamidbar Rabbah is not in the Talmud. It is in a separate category of work called Midrash.
As for the quote itself, it is purposely mistranslated to make Jews look bad.
The context of the quote is in the retelling of the story of Pinchas, who, in Numbers 25, slew the Jewish prince Zimri and the Midianate princess Kozbi for their role in causing the Jews to sin.
Here is the actual quote:
Note that the quote is talking about the wicked, not about non-Jews. This is further reinforced when you consider that one of the people Pinchas slew was a Jew.
It also should be pointed out that this is a homiletic teaching, and is not actual Jewish law. Jewish law is not derived from Midrash. We don’t go around killing sinners (Jewish or otherwise).
Summary:
This quote was purposely mistranslated to make it seem like Jews should go around killing non-Jews all the time. However, the subject matter here is the wicked, not non-Jews. And, on a practical level, this teaching is not followed.