How could God treat His people so differently in Old Testament times as compared to the New?  The Old Testament is full of long lists of rules and regs, along with severe penalties to be exacted upon those who break them.  The New Testament is all about grace and tells those in Christ they are free of the law.  What gives?

This is no big mystery.  The first part of the Old Testament was written for people who, for more than 10 generations, had lived as slaves.  After God sent Moses and arranged for their freedom, they obviously needed a bit of clearly defined structure.  The New Testament is about Jesus inviting us to become sons and daughters in God’s family.  For those who accept, He gives His Spirit as an internal guide, making rules irrelevant.

Ask yourself this question: Did you treat your two year old in the same way when he or she became 32?  I would imagine you began with rules, such as, “We never cross the street by ourselves.”  Later on, that rule changed to, “Always look both ways before you cross the street.”  And then, “‘Bye; Have a nice time!”

Here’s a great explanation of how God’s approach changed and why, taken from the New Testament:

I mean that the heir, as long as he is a child, is no different from a slave, though he is the owner of everything, but he is under guardians and managers until the date set by his father. In the same way we also, when we were children, were enslaved to the elementary principles of the world. But when the fullness of time had come, God sent forth his Son, born of woman, born under the law, to redeem those who were under the law, so that we might receive adoption as sons. And because you are sons, God has sent the Spirit of his Son into our hearts, crying, “Abba! Father!” So you are no longer a slave, but a son, and if a son, then an heir through God.  (Galatians 4:1-7  NIV)