Ezra had set his heart to study the Law of the LORD, to do it, and to teach statutes and rules in Israel. This sentence summarizes his mission and explains his work in Jerusalem. See Ezra 7:10.
Ezra arrives in Jerusalem in the fifth month of the king’s seventh year (Ezra.7.8). The passage then backs up to give the travel dates: he set out from Babylon on the first day of the first month and reached Jerusalem on the first day of the fifth month, with the journey credited to God’s favorable support (Ezra.7.9). These verses sit inside the narrative that introduces Ezra’s mission under a Persian king and prepares for what Ezra will do once he arrives.
Ezra 7:8–10 links Ezra’s arrival in Jerusalem to a precise public timeline and to a stated purpose. The text is clear that Ezra reached Jerusalem in the fifth month of the king’s seventh year, after beginning “to go up” from Babylon on the first day of the first month and arriving on the first day of the fifth month (a four-month span).
A careful answer keeps the immediate passage, the book's argument, and the whole-Bible storyline together, so the question is answered in context instead of as a detached idea.
Start with Ezra 7:10, then read the surrounding section so the answer stays connected to the passage's flow.
10For Ezra had set his heart to seek the law of Yahweh, and to do it, and to teach in Israel statutes and ordinances.