Albert Barnes Commentary Ezra 8:31

"Then we departed from the river Ahava on the twelfth [day] of the first month, to go unto Jerusalem: and the hand of our God was upon us, and he delivered us from the hand of the enemy and the lier-in-wait by the way." — Ezra 8:31 (ASV)

The Jews with Ezra left Babylon on the first day of the first month (Ezra 7:9). They reached Ahava in nine days, and, having remained there three days (Ezra 8:15), left it and resumed their journey on the twelfth. They reached Jerusalem on the first day of the fifth month (Ezra 7:9), four months after their departure from Babylon.