When God created man, He chose for Adam to represent his posterity as "federal head" in the covenant of works. Hosea 6:7 speaks of a covenant which Adam broke,
and Romans 5:12-19 implies that there was a covenant involved with Adam because he represents the human race. Isaiah 24:5 speaks of an everlasting covenant which is universal because it applies to the entire "earth"; this would also seem to
be a reference to a covenant made with all mankind.
Jesus Christ took man's place, fulfilling the covenant of works which Adam failed at, and thus Adam is an antitype of Christ. I Corinthians 15:45 speaks of Jesus as the "last Adam."