God is everywhere.
This simple idea changed the world because it meant the god of the Israelites did not reside just on a mountaintop in Jerusalem--he could live along the banks of the Euphrates, on the shores of the Nile, or alongside any river or mountain, anyplace in the world. This notion could have been a mere platitudinous response to the crisis, but it took hold because of how the Israelites responded to their national trauma. The towering significance of what happened by the rivers of Babylon is that the Israelites did not merely weep; they set about redefining what it meant to worship God. They invented Judaism.
The exact details of this birthing are not clear. Some of the exiled Judaeans clearly began to worship other gods; some seem to have suggested rebuilding the Temple in Babylon. But the majority seem to have understood that the bulk of their practices from Jerusalem were dead and that they needed new ways to honor, debate, and interact with God. One idea they adopted was to gather in small groups and discuss the words of the Lord. These congregations, "by the walls and in the doorways of their houses," as Ezekiel puts it, were temporary human sanctuaries that could replace the displaced holy sanctuary. These congregations were also more populist than the Temple in Jerusalem, which was limited to the priests. Later these sanctuaries would mature into synagogues.
Another custom that rose to prominence was celebrating the Sabbath. The idea of taking one day a week to rest, renew, and honor God goes back to the first wilderness experience in the Sinai. But as Jeremiah notes, the tradition never stuck: "They would not listen or turn their ear; they stiffened their necks and would not pay heed or accept discipline." So the prophets trot out the idea again and this time raise the stakes. As Isaiah notes, redemption now depends on obedience.
If you call the sabbath "delight,"
The Lord's holy day "honored";
And if you honor it and go not your ways
Nor look to your affairs, nor strike bargains-
Then you can seek the favor of the Lord.
With the loss of holy space, holy time becomes important.
But the sine qua non of this evolution was the elevation of text to the core of the faith. The importance of narrative and written law to Israelite religion had been emerging for many centuries, going back to the Ten Commandments, the first thing written down in the biblical story. This appreciation of recorded words continued to evolve through the monarchy, when portions of the written Bible began to enter Israelite public life. But the Exile accelerated this tendency. With no access to sacred sites, sacred text became Israel's lifeline to its past. As Jeremiah's letter to the exiles indicates, priests were becoming more important-and more focused on directly serving the population, not just worshiping God in the Temple. They began to edit the myriad of oral and written traditions of Israelite history and combined them into a unified canon. The Bible may not have been born in Babylon, but it certainly came of age here.