A.T. Robertson Commentary Matthew 6:16

"Moreover when ye fast, be not, as the hypocrites, of a sad countenance: for they disfigure their faces, that they may be seen of men to fast. Verily I say unto you, They have received their reward." — Matthew 6:16 (ASV)

Of a sad countenance (σκυθρωπο). Only here and Lu 24:17 in the N.T. It is a compound of σκυθρος (sullen) and οπς (countenance). These actors or hypocrites "put on a gloomy look" (Goodspeed) and, if necessary, even "disfigure their faces" (αφανιζουσιν τα προσωπα αυτων), that they may look like they are fasting. It is this pretence of piety that Jesus so sharply ridicules. There is a play on the Greek words αφανιζουσ (disfigure) and φανωσιν (figure). They conceal their real looks that they may seem to be fasting, conscious and pretentious hypocrisy.