Here is a shorter passage, paralleling the previous Matthew post nicely. Should make up for the length of the last one.
6.16 Ὅταν δὲ νηστεύητε, μὴ γίνεσθε ὡς οἱ ὑποκριταὶ σκυθρωποί· ἀφανίζουσιν γὰρ τὰ πρόσωπα αὐτῶν ὅπως φανῶσιν τοῖς ἀνθρώποις νηστεὐοντες· ἀμὴν λέγω ὑμῖν, ἀπέχουσιν τὸν μισθὸν αὐτῶν. 6.17 σὺ δὲ νηστεύων ἄλειψαί σου τὴν κεφαλὴν καὶ τὸ πρόσωπόν σου νίψαι, 6.18 ὅπως μὴ φανῇς τοῖς ἀνθρώποις νηστεύων ἀλλὰ τῷ πατρί σου τῷ ἐν τῷ κρυφαίῳ· καὶ ὁ πατήρ σου ὁ βλέπων ἐν τῷ κρυφαίῳ ἀπδώσει σοι.
6.16 And when you fast, don’t be gloomy like the “pretenders”; for they put on sour faces so that they may appear to men to be fasting; Truly I say to you, they have received their reward in full. 6.17 But when you fast, anoint your head and wash your face, 6.18 so that you will not appear to men to be fasting – but instead to your Father in secret; and your Father seeing in secret will repay you.
In 6:16, we find the word ἀφανίζουσιν, which is often translated, “to disfigure.” Interestingly, this word will be used in again in the next section, and means there, “to remove.” At root it means to cause to vanish, hide, keep out of sight, to destroy, to “render unsightly”. (The future passage uses the word to speak of moths which will cause things laid up in storage to vanish, be destroyed, be made unsightly.) This one speaks of men who have made themselves appear unhappy. They have a bad look about them, purposeful, that men might know they were fasting. Why fast if no one is going to know about it?
Of course, God is the only one who needs know.
And following in verse 17, Jesus instructs his listeners that they should anoint their head and wash their face. I would take this to mean that not only were the hypocrites putting on bad expressions, they were letting themselves get nasty as a means of standing out. They were doing everything possible to seem out of sorts. This kind of self-righteous posturing should make you sick, as it certainly made Jesus so. In words unmistakable, Jesus tells them to prepare themselves as if they were in the best of moods, with everything going for them.
Once again the emphasis is on the Father who sees in secret. Once again Jesus says that those who follow his words will be “repaid”. Once again, this is not a material payment, but instead a balance transfer, or maybe better yet, a stock purchase. Rather than receive immediate payback with men, fasting for only God to see will be repaid in a rich relationship with God that has its eternal reward.
Actually, at first I was sort of amazed at how little Jesus says here about fasting. More will be said in the Gospels, but here Jesus is quite brief, merely expressing an expectation that fasting will occur, and the conditions that God will honor when we are fasting. He is not trying to lay out a doctrine of fasting. There is an assumed understanding of fasting and its purpose. Rather, he is once again teaching his followers exactly what he meant when he said they must exceed the righteousness of the scribes and Pharisees. Their bad example provides the illustration he needs to share God’s heart.