“At that time those who had come from captivity, the returned exiles, offered burnt offerings to the God of Israel, twelve bulls for all Israel, ninety-six rams, seventy-seven lambs, and as a sin offering twelve male goats. All this was a burnt offering to Yahweh. They also delivered the king’s commissions to the governors of the province Beyond the River. They supported the people and the house of God.”
This group then got together. They offered burnt offerings to God for their successful return to Jerusalem. This included 12 bulls, 96 rams, 77 lambs, and 12 goats. Notice the 12 bulls and 12 goats as a remembrance of the 12 now non-existant 12 tribes of Israel. This was a burnt offering. Notice the change from a first person narrative to a third person explanation. They also reported to the governors of the Province Beyond the River, which would have been in Samaria. Meanwhile they supported the people there and the Temple.
“On the fourteenth day of the first month the returned exiles kept the Passover. For both the priests and the Levites had purified themselves. All of them were clean. So they killed the Passover lamb for all the returned exiles, for their fellow priests, and for themselves. It was eaten by the people of Israel who had returned from exile. It was eaten also by all who had joined them and separated themselves from the pollutions of the nations of the land to worship Yahweh, the God of Israel. With joy, they celebrated the festival of unleavened bread seven days. Yahweh had made them joyful. He had turned the heart of the king of Assyria to them, so that he aided them in the work of the house of God, the God of Israel.”
There is an assumption that this Passover took place after the dedication of the Temple since the purification process could take place, putting this time in 515 BCE or 417 BCE. All who took part in the Passover were clean because they had purified themselves by offering sacrifices at the Temple altars. The Passover was for the returned exiles and anyone who had separated themselves from the polluted gods of Israel. They also celebrated the 7 day festival of unleavened bread. There is a comment about the king of Assyria, but it was the king of Persia who was kind to them