What the writer says here regarding Josiah is nearly the same as what he said regarding Hezekiah in 2 Kgs 18.5.

The expression turned to the LORD implies service to Yahweh. Some other possible renderings are “came back to the Lord’s allegiance” (Knox), “adhered to the Eternal” (Moffatt), and “was so attached to the Lord” (Bible en français courant).

With all his heart and with all his soul and with all his might: This combination of words is strikingly similar to the injunction to obedience in Deut 6.5. It is also similar to certain New Testament passages (Matt 22.37; Mark 12.30; Luke 10.27). The heart is the seat of the emotions. It is possible to understand the word rendered soul as referring to the “mind” in this context. See the comments on heart and soul in verse 3. The word might may be also accurately translated “strength.” The expression as a whole represents Josiah’s absolute devotion to serve the LORD according to the Law.

According to all the law of Moses: This expression implies careful and complete obedience to the Law. Some may prefer to translate “following all that the Law of Moses teaches” or “doing everything that is required in the Law of Moses.”

The verb arise followed by the preposition after yields the meaning “to succeed” or “to follow” in the sense of one ruler coming after another.

The words Before him at the beginning of the verse and after him at the very end serve as a kind of envelope, but such a structure may be unnatural in other languages. It may be particularly difficult to place the words Before him at the very beginning of the sentence as Revised Standard Version has done.

Quoted with permission from Omanson, Roger L. and Ellington, John E. A Handbook on 1-2 Kings, Volume 2. (UBS Helps for Translators). New York: UBS, 2008. For this and other handbooks for translators see here .