Hebrews 7:15

κατάδηλον. The word used is stronger than πρόδηλον in Hebrews 7:14 and does not occur elsewhere in the N.T. The change of the Law can be yet more decisively inferred from the fact that Melchisedek is not only a Priest of a different tribe from Levi, but a priest constituted in a wholly different manner, and even—as he might have said—out of the limits of the Twelve tribes altogether; and yet a Priest was to be raised after his order, not after that of Aaron.

εἰ. Followed by the present indicative εἰ means “if” (as is the case), i.e. “seeing that.”