OLD TESTAMENT ... NEW TESTAMENT ... SAME GOD.
If you are not familiar with the Ignatius Catholic Study Bible by Scott Hahn and Curtis Mitch, you are missing a great tool for understanding our Faith and your Bible. For Matt. 5 they quote Augustine right away and essentially say the OT law given to Moses on Sinai was a lesser law- given to a people who needed threats ("bonds of fear") in order to obey, but Jesus' law is a higher law, for "those ready to be set free by love". Then they add, "The higher precepts are for the Kingdom of Heaven, just as the lower precepts were for a kingdom on earth". Augustine! I guess some people need the "bonds of fear" because they are not ready for Love to move them. But if the bonds of fear become our MAIN tool in ministry, we are not up on the mountain, listening to Jesus, but down at the bottom of the mountain, sitting on a rock with our 2 by 4 "smacker" waiting to convince the crowd that Love is NOT everything...... not entering Love's narrow way ourselves, and, God forbid, maybe preventing others from entering.