Easton's Bible Dictionary: M. G. Easton, M.A., D.D.
The practice common among Oriental nations of colouring the forehead or impressing on it some distinctive mark as a sign of devotion to some deity is alluded to in Rev. 13:16,17, 14:9, 17:5, 20:4
The "jewel on thy forehead" mentioned in Ezek. 16:12 (R.V., "a ring upon thy nose") was in all probability the "nose-ring" (Isa. 3:21).
In Ezek. 3:7 the word "impudent" is rightly rendered in the Revised Version "an hard forehead." (See also ver. 8,9.)
Original from The Bible Foundation - bf.org. They claim public domain status for their original text.