According to the custom — It is necessary here to read Deuteronomy 16; Leviticus 23; Numbers 29 The intention obviously is to lay stress on the provision made for an entire renewal of the Mosaic economy of service, as appears in the next verse.
Related Commentaries of Ezra 3:4
Ezra 3:4
4 They kept also the feast of tabernacles, as it is written, and offered the daily burnt offerings by number, according to the custom, as the dutyb of every day required;