(chazaq, qashah; skleruno):

(2) "Harden" in the sense of "to fortify one’s self" (make one’s self hard) is the translation of caladh, "to leap," "exult" (Job 6:10 the King James Version, "I would harden myself in sorrow," the Revised Version (British and American) "Let me exult in pain," margin "harden myself").

(3) In Pr 21:29 "harden" has the meaning of "boldness," "defiance" or "shamelessness" (brazen-faced); `azaz, Hiphil, "to strengthen one’s countenance," "A wicked man hardeneth his face"; Delitzsch, "A godless man showeth boldness in his mien"; compare Pr 7:13; Ec 8:1; see also HARD.

For "harden" the Revised Version (British and American) has "stubborn" (Ex 7:14; 9:7, margin "heavy"); "hardenest" (Isa 63:17); "made stiff" (Jer 7:26; 19:15); for "is hardened" (Job 39:16, the American Standard Revised Version "dealeth hardly," and the English Revised Version margin); "at the hardening" instead of "for the hardness" (Mr 3:5); "hardening" for "blindness" (Eph 4:18).