ISB ~ Hebrews 7 v3

without father … mother:Not literally, but in contrast to the requirements for priestly ministry in Israel, where a prospective candidate had to show proof of Aaronic descent on his father’s side and a compatible genealogy on his mother’s side. Failure to meet these requirements rendered aspiring men ineligible for priestly service (Ezra 2:61-63; Neh 7:63-65). Neither Melchizedek nor Jesus was bound by these restrictions; indeed, neither had a Levitical genealogy (Heb 7:6, 14). Some take the silence of Scripture about the life-span and parents of Melchizedek as an allegorical sign of the eternal generation of God the Son. This is a valid theological point, but it is not the point being made in Hebrews. neither beginning …

nor end:Not literally, but in contrast to the age limits set for the Aaronic priesthood, where ministry began at 30 and ended at 50 (Num 4:3, 43). Melchizedek was not limited to two decades of ministry, for no such age restriction was in force in pre-Levitical times. Jesus likewise exercises his priesthood for as long as he lives— for ever (Heb 7:24).

for ever:The Greek expression here is both different and weaker than the one translated “for ever” in 6:20 and 7:17, 21, 28. The sense is that Melchizedek was priest “for a long time”, whereas Jesus remains a priest “for all eternity”.