Charles Ellicott Commentary 2 Chronicles 18:21

"And he said, I will go forth, and will be a lying spirit in the mouth of all his prophets. And he said, Thou shalt entice him, and shalt prevail also: go forth, and do so." — 2 Chronicles 18:21 (ASV)

And be. — Become (wĕhâyîthî lĕ). Kings omits the particle.

A lying spirit. — A spirit of falsehood. (Isaiah 19:14; Ezekiel 14:9: And the prophet, if he be deceived, and speak a word, it is I, Jehovah, who have deceived that prophet. The verb “deceive” is the one rendered “entice” here and in 2 Chronicles 18:19, pittah. Septuagint, Ἀπατήσεις (See also 2 Thessalonians 2:11).)