Orthodox Jews trust themselves only to the first five books of the Bible, the Torah, while other Jews look to something much more like what we consider to be the Old Testament, but still with a very strong emphasis on the Torah, the psalms, and the historical books.  All of this, generally speaking, is the Law. 

In Exodus 24:3-8 Moses bound the people to the Law by a covenant, the particular one which we refer to in the expression “Old Testament,” and which has a very direct effect on the words we use in the consecration of the Eucharist. 

Over the years, rabbis in every age and place have examined those Old Testament texts, and their interpretation of the Law has gained almost the force of the Law all by itself.  All of this gives great certainty about knowing God's will and the kind of comfort that can come from that certainty.

Today's reading from Jeremiah is very clear in stating that such confidence is misleading, that there is another and complementary Law, a New Covenant to complete the Mosaic covenant.  This is the law of the Spirit, calling us not to what we must do but to an attentiveness and  generosity that allows us to follow God in every situation, not only those spelled out in the Law.  This is a different sort of obedience, not a blind obedience but a mature and personal one which seeks a God who never stops leading us forward.  

We Christians live not in absolute obedience to a written Law, especially not one spelled out in such detail; as much as we can and as imperfect as our efforts may be, we put ourselves in the hands of our Father, imitate His Son, and follow the Spirit.  This calls for very personal prayer, the kind of poverty of self which the Beatitudes call for (Matthew 5:1-12), and a life rooted in the cardinal virtue of hope.