It was quite the mystery of the universe. Sin had destroyed the lovely Garden of Eden relationship Adam and Eve had with Creator God. So God established a “covenant of forgiveness”, a system of sacrifice whereby His followers could be forgiven.
But it was obvious that we on earth could not go on for all of eternity sacrificing lambs for the forgiveness of sins. What did God have in the works? It remained a mystery for centuries. And then, finally, according to His perfect timing, He revealed the answer.