Komentaryong Sumisipi para sa Mga Kawikaan 21:29

“In number, forty shall strike him.” They whip him two-thirds from behind and one-third from the front (Makkot 23) because every sinner turns his back to the Divine Presence and treats the Eye above as if it does not see. And there are sinners who brazenly face God, as it is written A wicked man hardens his face (Proverbs 21:29). And just as the Torah was stricter with a thief than with a robber, imposing double payment upon him because he denies the Eye above and does not [even] equate the servant and his Master, which is not the case with a robber (Bava Kamma 79b), so too double [punishment] is imposed upon him — to be lashed twice as much from behind and one part from the front, because with every sin there is doubt whether he brazenly faced [God] or whether he turned his back to God, in which case his sin is doubled.

THE BRAZEN [lit. “strong of face”] END IN GEHINNOM. For he brazenly violates the will of his Father in Heaven. Rav writes that brazen people are called “strong of face” based on the verse in Proverbs 21:29, “an evil man’s brazenness is on his face.” And the verse says, “the wicked will return to Sheol” (Psalms 9:18).

"brazen-faced": Since brazenness is noticeable in the face, as it is written (Proverbs 21:29), "The brazenness of an evil man is in his face": therefore he is called brazen-faced.