The first Adam would have been declared righteous (meaning: having earned eternal life) by his obedience to the command of God (Law of Creation) under which he was created. Like unto Israel later, in the environs of a holy mountain, the first Adam in Eden received this Law of God (see Ezk 28:13-16, where Eden is described as being a ‘holy mountain’). Thus, Adam profaned the holy realm as did national Israel; all of which, set the stage for the messianic service/suffering of Christ. The purpose of Israel’s national existence was two-fold: 1) To exhaustively confirm that human nature was indeed corrupt and guilty in Adam. a) Israel illustrated in their perpetually idolatrous stubbornness;
b) Israel as a nation acted as something of an Adamic-corpse—upon which the Mosaic Law acted as a scalpel in the hand of God—for an autopsy to be performed before all the world, confirming its (Israel and the World’s) image in fallen-Adam.
2) To set the historical-stage for God’s redemptive-act in the Christ, the Second Adam.a) For so it was…the Law was added to increase Adam’s one transgression (Rom 5:20), until the Offspring should come (Gal 3:19)b) Who, being born under the Mosaic Law, would uphold the Law (Gal 4:4-5) for:i. His righteousness sake (confirming He was righteous by keeping the Law perfectly, according to strict justice), andii. Our unrighteousness sake (conquering Adamic sin by coming under the curse of the Law willingly, Gal 3:13)