Whole-hearted

“But you did not listen to me,” declares the Lord, “and you have aroused my anger with what your hands have made, and you have brought harm to yourselves.”
Jer. 25:7

Note that not listening to the Lord does two things: It arouses His anger and it brings harm to yourself.  Neither are wise and the second automatically follows from the first.

2 Kings 16 — Here is the strange story of Ahaz, son of Jotham.  Jotham was an "okay" king doing right, but there were still the high places left in the land.  I wonder if these became a snare for his son Ahaz.  Regardless, Ahaz rejected true worship of YWHW and actively pursued any other form of religion that allowed him to do as he pleased.  But notice his syncretism:

   King Ahaz then gave these orders to Uriah the priest: “On the large new altar, offer the morning burnt offering and the evening grain offering, the king’s burnt offering and his grain offering, and the burnt offering of all the people of the land, and their grain offering and their drink offering. Splash against this altar the blood of all the burnt offerings and sacrifices. But I will use the bronze altar for seeking guidance.”
   2 Ki. 16:15

He believed in "both/and" and borrowed whatever from wherever.  He ended up with a different gospel, and would have been happy with a different Jesus and a different spirit.  He was half-hearted at best in his worship of the Lord; but half-hearted is worthless in God's estimation. 

God wants whole-hearted devotion:

• Ps. 9:1; 111:1 — whole-hearted praise of God
• Ps. 119:2, 10 —whole-hearted seeking of God
• Ps. 119:34, 69 — observe & keeps laws whole-heartedly
• Ps. 119:58, 145 — crying out to God, praying and pleading with Him whole-heartedly

We must remember that He is the rewarder of those that diligently seek Him.  (Heb. 11:6)