While pondering on the topic of blood atonement, I came across the following from the Encyclopedia Judaica:
KIDDUSH HA-SHEM . . . [implies]
the glorification of the God of Israel . . .
MARTYRDOM. The readiness to sanctify God’s Name
has its most dramatic expression in the willingness to die a martyr, and since
tannaitic times the term kiddush ha-Shem also denotes martyrdom (see below Historical Aspects). When a person
willingly suffers death rather than violate one of three specific commandments (see
below) he achieves kiddush ha- Shem; if he fails to do so in these cases, or in other instances where the halakhah
demands martyrdom, he is guilty of ḥillul ha-Shem (Av. Zar. 27b; Sanh. 74a, b). On the verses, “Ye shall not profane My
holy Name,… I am the Lord who hallow you, brought you out of the land of Egypt,
to be your God: I am the Lord” (Lev. 22:32, 33), the rabbis taught: “On this
condition did I bring you out of the land of Egypt that you submit yourselves
to sanctify My Name, that I be your God even by force; I the Lord am faithful
to grant you your reward” (Sifra, Emor, Perek 9). Since the second century, “to
die for the sanctification of the Name” has been the accepted idiom for dying a
martyr’s death. A martyr was, appropriately, called a kadosh, one who is holy. In time, this honorific was extended and applied as
well to those who died solely because they were Jewish even without their
consciously offering up their lives for religious purposes (Moshe Lamm, Darkah
shel ha-Yahadut be-Mavet u-ve-Avelut (2005), 221–222.) A child,
growing up in the Jewish tradition, was
exposed to the concept of martyrdom as an ideal. From his earliest youth he was taught stories about martyrs, e.g.,
*Hannah and her seven sons, R. *Akiva and the other of the *ten martyrs; the
latter in the form of a lamentation is part of the synagogue service on the
*Day of Atonement and on the Ninth of *Av. Hananiah, Mishael, and Azariah (Dan.
3) are held up by the rabbis as models of conduct in the sanctification of the
Name (Pes. 53b).
At the famous rabbinical
council in *Lydda (second century), the laws of martyrdom were formulated. Kiddush
ha-Shem was declared obligatory in the case of three
commandments and a person had to suffer death rather than violate them:
idolatry, unchastity (gillui arayot:
including incest, adultery, and, under certain circumstances, any infraction of
the code of sexual morality), and murder (Sanh. 74a). One should violate all
other commandments rather than suffer death. Should a Jew, however, in the
presence of ten other Jews, be coerced into transgressing these other laws in
order to demonstrate his apostasy, he must sanctify God’s Name and choose
death. If ten Jews are not present, he should transgress rather than be killed.
These rules hold for “normal” times. In times of religious persecution of the
entire community, however, one must choose to die for kiddush
ha-Shem even if no other Israelites are present, and
one must not violate any commandment, including minor customs which are
distinctively Jewish (Maim. Yad, Yesodei ha-Torah, 5:3). Martyrdom rather than
violation, when transgression is permissible, became a point of discussion; the
halakhah had
to decide between two opposing principles – that of sanctifying God’s Name
versus that of preserving life (“and he shall live by them” (Lev. 18:5), i.e.,
the commandments). According to Maimonides, a person who chose kiddush
ha-Shem where the law decides for life is culpable
(Maim. ibid., 5:1); others consider such
voluntary martyrdom praiseworthy (Tos. Av. Zar. 27b). The Ashkenazi talmudists
were instinctual rather than rationalistic in their attitude to martyrdom – an
attitude characteristic of most of medieval German Jewry. The tosafists reacted
negatively to the problem as it is viewed in the halakhah. They recoiled –“Heaven forbid!” – from such formal halakhic reasoning
that does not require martyrdom of a person forced to worship an idol in
private, and they demanded obligatory kiddush ha- Shem (Tos. Av. Zar. 54a). ("KIDDUSH HA-SHEM AND ḤILLUL
HA-SHEM," Encyclopedia Judaica, 21 vols. [2d ed.; Jerusalem: Keter
Publishing House, 2007], 12:139, 140-41)
This
is just me spit-balling, but perhaps this is a theological foundation for the
practice—one has blasphemed God in a way that requires, for His honour and
glory, a great sacrifice. Typically, it would be martyrdom by the righteous; in
the case of blood atonement, offering up a sacrifice of one’s life as (albeit,
an extreme form of) repentance.