The Israelites were taken captive by the Babylonian empire as the final act of God’s judgment against His sinful nation. They had turned to idolatry and trusted more in man than they did in God. They had rejected God from their lives and their hearts, so God rejected them. After 70 years in captivity, God’s people returned to their land. When the remnant returned, they did not want to make the same mistakes their parents had made. They wanted to make sure that they got it right this time and did what God wanted them do. So, how would they know what to do?
Read the books of Ezra and Nehemiah. The Israelites “built the altar…to offer burnt offerings on it, as it is written in the Law of Moses”; they “kept the Feast of Tabernacles, as it is written”; they “assigned the priests…and the Levites…over the service of God in Jerusalem, as it is written in the Book of Moses”; they made “booths, as it is written”; they burned “on the altar…as it is written in the Law”; they brought “the firstborn of sons and cattle, as it is written in the Law” (Ezra 3:2, 4; 6:18; Neh. 8:15; 10:34, 36). We can know what God wants, too, if we’ll obey Him, as it is written!