The returnees have their priorities correct; they first build the altar in order to offer sacrifices and worship to God. The author plunges quickly into the project at hand, and specifies the time (autumn of 537 BC). The seventh month, Tishri (our September–October), traditionally was important for its religious ceremonies. On the first of the month the New Year and Feast of Trumpets were celebrated (Lev. 23:23–25). Although not mentioned here, the Day of Atonement was the tenth day (Leviticus 16). From the fifteenth day until the twenty-first was the celebration of the Feast of Tabernacles, mentioned in verse 4.

There are several emphases here: (1) the unity and continuity of the community (“The people assembled as one man,” 3:1); (2) beginning by putting God first (worship); and (3) fo…