1 Kings 22:21

And there came forth a spirit The Hebrew has - thespirit" as is noted on the margin of the R.V. It seems therefore to imply some definite power which imparted to prophets their gifts; the prophetic spirit. That God allowed this power to delude Ahab was because of the king's persistence in evil. God therefore gives him over to it, and causes the prophets whom he has chosen for himself, to the rejection of Micaiah and such as he, to be the instruments of his destruction. Thus when Isaiah is sent to rebellious Israel (Isaiah 6:10) his mission is described as of this nature. God says to him -Make the heart of this people fat and make their ears heavy, and shut their eyes, lest they see with their eyes, and hear with their ears, and understand with their hearts." In this wise and with like effect comes the spirit from God into the mouths of Ahab's four hundred.