Jacob is considered the patriarch of the Israelites and his 12 sons were the heads of the 12 tribes of Israel. One of his sons was Levi and the descendants of Levi, or the Levites, are the ones Ra is referring to here.
Members of the Tribe of Levi had greater rights than members of the other tribes, and the ancient priestly caste of Israel, the Kohenim, were all drawn from the Levites. The other tribes payed tithe to the Kohenim and even the lay Levites had important ritual roles in the temple and were in charge of cities. Moses was a member of the Tribe of Levi as well.
Members of the Tribe of Levi had greater rights than members of the other tribes, and the ancient priestly caste of Israel, the Kohenim, were all drawn from the Levites. The other tribes payed tithe to the Kohenim and even the lay Levites had important ritual roles in the temple and were in charge of cities. Moses was a member of the Tribe of Levi as well.