"Then the people of Israel - The priests, the Levites and the rest of the exiles - celebrated the dedication of the house of God with joy. For the dedication of this house of God they offered a hundred bulls, two hundred rams, four hundred male lambs and, as a sin offering for all Israel, twelve male goats, one for each of the tribes of Israel." NIV translation
After the work was completed, they had a dedication ceremony. It is interesting to note that the sacrifices that were offered were not the same as the ones that were offered at the dedication of Solomon's temple. There were less sacrifices as there was only the remnant of God's people back in Jerusalem. We also see that a goat was offered for each of the tribes of Israel. There are some who refer to some of the tribes of Israel as "lost" but, as we see here, all of the tribes had a remnant at the dedication. The goats were what is known as scapegoats as the sins of the tribes were to be put on the goats.
"And they installed the priests in their divisions and the Levites in their groups for the service of God at Jerusalem, according to what is written in the Book of Moses." NIV translation
With this new temple, the people had decided to turn back to the word of God.
This included setting the proper people in place for the service in the temple.
"On the fourteenth day of the first month, the exiles celebrated the Passover. The priests and Levites had purified themselves and were all ceremonially clean. The Levites slaughtered the Passover lamb for all the exiles, for their brothers the priests and for themselves. So the Israelites who had returned from the exile ate it, together with all who had separated themselves from the unclean practices of their Gentile neighbors in order to seek the Lord, the God of Israel. For seven days they celebrated with joy the Feast of Unleavened Bread, because the Lord had filled them with joy by changing the attitude of the king of Assyria, so that he assisted them in the work on the house of God, the God of Israel." NIV translation
Now that the temple was restored, the people were able to celebrate the feasts of the Lord. They began with the Feast of Unleavened Bread (Passover) at its proper time. This was commanded by God after they left captivity in Egypt (see Exodus) as a reminder of the fact that God had delivered His people and spared their firstborn sons. This was the same feast that was happening when Jesus entered Jerusalem for the final time as our Passover lamb. Just as the king of Assyria had given the All Clear! signal to rebuild the temple, Jesus cleared the way for us to have a right relationship with God through His sacrifice.