Israels as priests

Israelites are regarded as a priestly nation. Their purity code is that of a dedicated order, and therefore it does not aply to the rest of mankind, who, however, can opt to become Jews, whereby they become liable to observe the purity laws and also, from the moment of conversion, contract and convey uncleanness. Rabbinic Judaism considers that all humanity, whether Jews or not, are in covenant with God and are bound to keep the laws of morality as summarized in the Seven Noachian Laws, the first code of international law. To become converted to Judaism is not a matter of salvation, but of dedication. Those who are born Jews must function as Jews, but for other members of humanity, Judaism is a choice; just as it is a choice for a Catholic to become a priest or a member of a monastic order, by which he will become a priest or a member of a monastic order...

The whole purity code found in the Torah and elaborated in the rabbinic literature is thus a protocol for a dedicated group living constantly in the presence of God, whose Tabernacle is in their midst. It is a kind of palace protocol or etiquette, observed in the court of a monarch, but not required outside the confines of the palace. Even for Jews, once the palace was destroyed, most of the rules became inoperative, though they continued to be studied...

The Hebrew bible knows nothing of unclean Gentiles or unclean Gentile lands.

(pp. 9-12, Hyam Maccoby, Ritual and Morality: The Ritual Purity System and its Place in Judaism