Albert Barnes Commentary Ezra 7:9

"For upon the first [day] of the first month began he to go up from Babylon; and on the first [day] of the fifth month came he to Jerusalem, according to the good hand of his God upon him." — Ezra 7:9 (ASV)

The direct distance of Babylon from Jerusalem is about 520 miles; and the circuitous route by Carchemish and the Orontes valley, which was ordinarily taken by armies or large bodies of men, is about 900 miles. The time occupied in the journey is long, and is perhaps to be accounted for by the dangers alluded to in (Ezra 8:22), (Ezra 8:31).