Luke 1:36

Thy cousin Elisabeth,— Mary and Elisabeth might be cousins, as the text affirms, although the former was a descendant of David, and the latter a daughter of Aaron: because the law, Numbers 36:6 forbidding women to marry out of their own tribes, related only to heiresses, and consequently did not include the tribe of Levi, which had no particular heritable possessions that could be alienated by such marriages. Accordingly, in Leviticus 22:12 it is supposed as a common case, that a priest's daughter might be married to a stranger. It is remarkable, that Gabriel does not refer the virgin to Sarah or Rebekah, examples in former ages, but to a present one; and to magnify and heighten the miracle, he adds, that Elisabeth was advanced in years, and, what was more, never had a child.