Kings III 22:22

22 And the Lord said to him, Whereby? And he said, I will go forth, and will be a false spirit in the mouth of all his prophets. And he said, Thou shalt deceive him, yea, and shalt prevail: go forth, and do so.

Kings III 22:22 In-Context

20 And the Lord said, Who will deceive Achaab king of Israel, that he may go up and fall in Remmath Galaad? and one spoke one way, and another another way.
21 And there came forth a spirit and stood before the Lord, and said, I will deceive him.
22 And the Lord said to him, Whereby? And he said, I will go forth, and will be a false spirit in the mouth of all his prophets. And he said, Thou shalt deceive him, yea, and shalt prevail: go forth, and do so.
23 And now, behold, the Lord has put a false spirit in the mouth of all these thy prophets, and the Lord has spoken evil against thee.
24 And Sedekias the son of Chanaan came near and smote Michaias on the cheek, and said, What sort of a spirit of the Lord spoken in thee?

The Brenton translation of the Septuagint is in the public domain.