Jehoshaphat was a good king. He did things that even good kings before him hadn't done. Not the least of which was the spiritual growth of Jehoshaphat as he learned the ways of God (2nd Chronicles 17:6). Jehoshaphat became so energetic in his walk with the Lord that he evidently began to realize just how imperative and valuable it would be to spread that spiritual wealth throughout his kingdom. So, he did that (2nd Chronicles 17:7, 8 & 9). He sent circuit riding teachers and preachers throughout the land to educate his people. And, oh how wonderful was the effect and impact of the knowledge of God's Word among the people. The success and holiness in Judah caused the people around them to respect and fear Jehoshaphat and his people to such an extent that they could even live in peace.
There is something that is particularly interesting to me in the sequence of the events that are covered in this chapter.
Consider what preceded this revival... and what followed it. The free growth of the knowledge of the truth was preceded by a moral cleansing of the land. Call it... repentance. Jehoshaphat removed the high places and groves out of Judah (2nd Chronicles 17:6). There was only one proper place to worship Jehovah in Judah, and it certainly was not in the various groves... groves which hearkened back to times when idolatry had prevailed. The temple was the proper hub for those sanctified activities.