The people with Baruch wanted to take up a collection and send money to the people in Jerusalem. With this money, the Jerusalem Judeans were to buy burnt offerings, sin offerings, incense, and grain offerings. All these were to be presented at the altar of the Lord God. However, there are some problems since the Temple and its altars were all destroyed. Was there a temporary temple in Jerusalem during the exile? How many people were left in Jerusalem?
Apparently, this gathering was with all the Judean exiles, and not any Babylonians. There, after the reading, they wept, fasted, and prayed to the Lord. After that, they took up a collection for the people who were left behind in Jerusalem. They were going to send it to the now high priest and the priests left in Jerusalem, Jehoiakim, the son of Hilkiah, the son of Shallum. There was no indication of how this money would get there. It was a free will offering, with each one giving what they could.