=The law to be written on the heart.=--Jeremiah saw that this mistake had come from relying too much on a written law. Something more than an outward law was needed before men could succeed in living together as brothers. It is so easy to keep the letter of the law, or to think one is keeping it, while we lose the spirit of it. What is needed, Jeremiah said, is a changed heart. Again and again he cried to the people, "Oh Jerusalem, cleanse thy _heart_." And in one of the great chapters of the Bible, the thirty-first of the book of Jeremiah, he looks forward to a time when Jehovah and his people should be bound together in a new covenant--not a covenant written on tables of stone like the one which Moses wrote at Sinai: ="But this is the covenant that I will make ... after those days, saith the Lord. I will put my law in their inward parts, and in their hearts I will write it."= The apostle Paul saw this promise fulfilled by the love which Jesus Christ awakens in men's hearts, so that they gladly and eagerly do the will of God. On account of this prophecy of Jeremiah our Christian Bible is called the New Covenant, or (from the Latin) the New Testament. JEREMIAH AND THE BABYLONIANS In Jeremiah's time (a decade or so before and after B.C. 600) the Babylonians had taken the place of the Assyrians as the rulers of the world. There was a powerful king, Nebuchadrezzar, on the throne of Babylon. And the existence of the kingdom of Judah depended on submission to him. But, just as in Isaiah's time a century before, there was now a party in Jerusalem who were constantly plotting to rebel against the Babylonians, hoping for help from Egypt. =Jeremiah as a patriot.=--Jeremiah had no sympathy with them. He loved his native land deeply and tenderly. But until the people were _worthy_ of liberty he was sure Jehovah would not give it to them. Again and again they proved their unworthiness. Once when the Babylonian armies were knocking almost at the gates of Jerusalem they remembered that law about Hebrew slaves, which had been made even more strict in the new law, Deuteronomy. According to this law, no Hebrew could be kept in slavery longer than seven years. So in their fear of the Babylonians these rich nobles solemnly set free a great number of slaves whom they had been illegally keeping in slavery. A few days later the hostile army, for some reason or other, withdrew. And within a month all these slaves who had been set free were seized and reenslaved. How Jeremiah denounced this hypocrisy! THE DESTRUCTION OF JERUSALEM If Jeremiah's advice had been followed, the people of Judah would have been spared a world of sorrow. But the leaders of the kingdom seemed bent on dragging the whole nation into ruin. In B.C. 597, Jerusalem was captured and some ten thousand of the inhabitants were carried away as exiles to Babylon.