Supersessionism in the context of "Christian observances of Jewish holidays"

The term Judeo-Christian is used to group Christianity and Judaism together, either in reference to Christianity's derivation from Judaism, Christianity's recognition of Jewish scripture to constitute the Old Testament of the Christian Bible, or values supposed to be shared by the two religions. The term Judæo Christian first appeared in the 19th century as a word for Jewish converts to Christianity. The term has received criticism, largely from Jewish thinkers, as relying on and perpetuating notions of supersessionism, as well as glossing over fundamental differences between Jewish and Christian thought, theology, culture and practice.

In the United States, the term was widely used during the Cold War in an attempt to invoke a unified American identity opposed to communism.

The Hebrew Bible makes reference to a number of covenants (Hebrew: בְּרִיתוֹת) with God (YHWH). These include the Noahic Covenant set out in Genesis 9, which is decreed between God and all living creatures, as well as a number of more specific covenants with Abraham, the whole Israelite people, the Israelite priesthood, and the Davidic lineage of kings. In form and terminology, these covenants echo the kinds of treaty agreements existing in the surrounding ancient world.

The Book of Jeremiah, verses 31:30–33 says that YHWH will establish a new covenant with the house of Israel and the house of Judah. Most Christians believe this New Covenant is the "replacement" or "final fulfilment" of the Old Covenant described in the Old Testament and as applying to the People of God, while some believe both covenants are still applicable in a dual covenant theology.

Throughout history, various groups of people have seen themselves as the chosen people of a deity, for a particular purpose. The phenomenon of "chosen people" is well known among the Israelites and Jews, where the term (Hebrew: עם סגולה / העם הנבחר, romanized: am segulah / ha-am ha-nivhar) refers to the Israelites as being selected by Yahweh to worship only him and to fulfill the mission of proclaiming his truth throughout the world. Some claims of chosenness are based on parallel claims of Israelite ancestry, as is the case for the Christian Identity and Black Hebrew sects—both which regard themselves (and not Jews) as the "true Israel". Others see the concept as spiritual, whereby individuals who genuinely believe in God are considered to be the "true" chosen people, "the elect". This view is common among many Christian denominations which historically believed that the church replaced Israel as the people of God.

Anthropologists commonly regard claims of chosenness as a form of ethnocentrism.

Anti-Judaism denotes a spectrum of historical and contemporary ideologies that are fundamentally or partially rooted in opposition to Judaism. It encompasses the rejection or abrogation of the Mosaic covenant and advocates for the supersession of Judaism and Jewish identity by proponents of other religious, political-ideological, or theological frameworks, which assert their own precedence as the "light unto the nations" or as the chosen people of God. The opposition is often perpetuated through the reinterpretation and appropriation of Jewish prophecy and texts, reflecting a complex interplay of belief systems that challenge Jews' internally and externally conceived distinctiveness. David Nirenberg posits that the theme has manifested throughout history, including in contemporary and early Christianity, Islam, nationalism, Enlightenment rationalism, and in socioeconomic contexts.

Douglas R. A. Hare found at least three anti-Judaisms in history. The first is prophetic anti-Judaism: the criticism of Judaism's beliefs and religious practices. The second is Jewish Christian anti-Judaism: the form taken amongst Jews who believe that Jesus of Nazareth was the Jewish Messiah. The third type he defined was gentilizing anti-Judaism, which emphasizes the gentile character of the new movement (i.e., Christianity) and asserts God's formal rejection of Jews as a people. Most scholarly analyses appear concerned with the phenomenon described by his third type.

Dual-covenant or two-covenant theology is a school of thought in Christian theology regarding the relevance of the Hebrew Bible, which Christians call the Old Testament.

Most Christians hold that the Old Testament has been superseded by the New Covenant, although the moral law continues to apply (cf. covenant theology); in contrast, a minority hold that the Mosaic covenant has been abrogated. Dual-covenant theology is unique in holding that the Mosaic covenant remains valid for Jews while the New Covenant only applies to non-Jews or gentiles.