Ezra 3:1–3 (ESV)

1 When the seventh month came, and the children of Israel were in the towns, the people gathered as one man to Jerusalem.

At the appropriate time, the people of Israel gather together in order to begin building the structures they need in order to worship God. Their first task is to build an altar that can be used to offer sacrifices. They build the altar in the manner that God’s Word requires of them and immediately begin offering the prescribed sacrifices. In doing this, the people demonstrate their eagerness to once again meet with God.