Albert Barnes Commentary Ezra 5:3

"At the same time came to them Tattenai, the governor beyond the River, and Shethar-bozenai, and their companions, and said thus unto them, Who gave you a decree to build this house, and to finish this wall?" — Ezra 5:3 (ASV)

Governor on this side the river - Compare the note on Ezra 4:10. Tatnai was apparently satrap of Syria, which included the whole tract west of the Euphrates from Cilicia to the borders of Egypt. Zerubbabel must have been, to some extent, under his authority.

Who hath commanded you to build? - There was no doubt a formal illegality in the conduct of Zerubbabel and Jeshua, since all edicts of Persian kings continued in force unless revoked by their successors. But they felt justified in disobeying the decree of the Pseudo-Smerdis (see the note on Ezra 4:7), because the opposition between his religious views and those of his successor was widely known.