There is still one prophet through whom we can inquire of the Lord, but I hate him because he never prophesies anything good about me

2 Chronicles 18:1-33

Now Jehoshaphat had great wealth and honor, and he allied himself with Ahab by marriage.

 So the king of Israel brought together the prophets—four hundred men—and asked them, “Shall we go to war against Ramoth Gilead, or shall I not?” “Go,” they answered, “for God will give it into the king’s hand.”

But Jehoshaphat asked, “Is there no longer a prophet of the Lord here whom we can inquire of?”

The king of Israel answered Jehoshaphat, “There is still one prophet through whom we can inquire of the Lord, but I hate him because he never prophesies anything good about me, but always bad. He is Micaiah son of Imlah.”

“The king should not say such a thing,” Jehoshaphat replied

So the king of Israel called one of his officials and said, “Bring Micaiah son of Imlah at once.”

Now Zedekiah son of Kenaanah had made iron horns, and he declared, “This is what the Lord says: ‘With these you will gore the Arameans until they are destroyed.’”

But Micaiah said, “As surely as the Lord lives, I can tell him only what my God says.”

The king said to him, “How many times must I make you swear to tell me nothing but the truth in the name of the Lord?”  Then Micaiah answered, “I saw all Israel scattered on the hills like sheep without a shepherd, and the Lord said, ‘These people have no master. Let each one go home in peace.’”

So now the Lord has put a deceiving spirit in the mouths of these prophets of yours. The Lord has decreed disaster for you.”

The king of Israel then ordered, “Take Micaiah and send him back to Amon the ruler of the city and to Joash the king’s son, and say, ‘This is what the king says: Put this fellow in prison and give him nothing but bread and water until I return safely.’”

Micaiah declared, “If you ever return safely, the Lord has not spoken through me.” Then he added, “Mark my words, all you people!”

But someone drew his bow at random and hit the king of Israel between the breastplate and the scale armor. The king told the chariot driver, “Wheel around and get me out of the fighting. I’ve been wounded.” All day long the battle raged, and the king of Israel propped himself up in his chariot facing the Arameans until evening. Then at sunset he died.

Why?

The Lord uses his servants to say words of the Lord, no one can deceive the Lord.

How 

To be a servant of the Lord say the truth only, do not be afraid of the authority of human beings, and this is hard to a real servant of the Lord. But I know the authority beyond anyone, so do not be afraid man.