Bob, the ministry Jesus received was the priesthood according to the order of Melchizedek, who was a priest of the God Most High( Heb. 7:1). This Melchizedek was “without father, without mother, without genealogy, having neither beginning of days nor end of life, but made like the Son of God who remains a priest continually.”(Heb. 7:3). Hebrews 7:15-16 "“And yet it is far more evident if, IN THE LIKENESS of Melchizedek, there arises another priest ( Jesus) who has come, not according to the law of fleshly commandment, but according to the power of endless life.”
Again, Gen. 17:7 says, “And I will establish My covenant between Me and you and your descendants after you in their generations, for an EVERLASTING covenant to be God to you and your descendants after you.”
Gen. 18:19 “For I have known him (Abraham), in order that he may command his children and his household after him, that they keep the way of the Lord, to do righteousness and justice, that the Lord may bring to Abraham what He has spoken to him.”
I’m not exactly sure, but my guess is that the text you cite( Luke 7:28) is a comparison between the kingdom of men( born of the flesh) and the kingdom of God ( born of the Spirit).
According to Gal. 4: 21-31, there were two covenants, as it says Abraham had two sons. One was born according to the flesh(the laws and doctrines of man), the other according to the Spirit( the Laws of God).Verse 29 “But , as he who was born according to the flesh then persecuted him who was born according to the Spirit, even so it is now.”
The Jewish law did not come about until the time of Moses. Prior to that, there was no Jewish law. This is the point that Paul is trying to make when speaking of the law. Abraham, Isaac,Jacob etc. didn’t have to follow the Jewish law to be righteous before God. They didn’t have to sit in the mikveh, go to a priest and sacrifice animals for forgiveness of sins, perform ceremonies and rituals, eat only certain foods, etc. etc. They simply followed the Spirit of God and the Law of Him that is written in the heart and mind.