The days are surely coming, says the Lord, when I will make a new covenant with the house of Israel and the house of Judah. It will not be like the covenant that I made with their ancestors when I took them by the hand to bring them out of the land of Egypt—a covenant that they broke, though I was their husband, says the Lord. But this is the covenant that I will make with the house of Israel after those days, says the Lord: I will put my law within them, and I will write it on their hearts; and I will be their God, and they shall be my people. No longer shall they teach one another, or say to each other, “Know the Lord,” for they shall all know me, from the least of them to the greatest, says the Lord; for I will forgive their iniquity, and remember their sin no more.
“Everyone then who hears these words of mine and acts on them will be like a wise man who built his house on rock. The rain fell, the floods came, and the winds blew and beat on that house, but it did not fall, because it had been founded on rock. And everyone who hears these words of mine and does not act on them will be like a foolish man who built his house on sand. The rain fell, and the floods came, and the winds blew and beat against that house, and it fell—and great was its fall!”
Jeremiah, writing at a time of great stress for Israel, speaks of an era to come when God will renew God’s covenant with the people. It will “not be like” the old covenant (the laws given on Sinai) but will come in a new form: an inner form. “I will put my law within them,” God says. The old external authorities are now balanced with a kind of internal authority. This should not be taken to mean completely individual moral autonomy, but it implies that the community will find within its corporate heart the guidance necessary to live a fruitful and faithful life.
In the passage from Matthew (yet another portion of the Sermon on The Mount), we encounter a very familiar image: building one’s house on sand or rock. Put together with the Jeremiah reading, this passage leads to consider what kind of moral “foundation” is necessary for a lasting, abundant life.
What does it mean to have God’s law written in one’s heart? Is this what we mean when we use the word “conscience”? How does this law get there? How do we get it, inherit it, acquire it? How do we know that it is God’s commandment and not just our own desires? In what ways are God’s commandments eternal, and in what ways are they time-conditioned? Taking all of this into account, what is our motivation for being good? Why bother?