Jesus Teaches about Fasting
This last act of worship, fasting, is a little bit different than the other’s we’ve talked about: giving or praying. God wants you give and He wants you to pray. Those are commands. But you know what, I don’t think God really cares if you fast or not. What he wants is your complete devotion. And at times, that devotion may be so focused that you don’t care about eating. And that honors God—not because you went hungry, but because you evidently cared so much about him that food—something you need to survive—was just not that important to you.
Matthew 6:16-18 “When you fast, do not look somber as the hypocrites do, for they disfigure their faces to show others they are fasting. Truly I tell you, they have received their reward in full.
But when you fast, put oil on your head and wash your face,
so that it will not be obvious to others that you are fasting, but only to your Father, who is unseen; and your Father, who sees what is done in secret, will reward you.
Jesus’ statement when you fast (cf. Matt. 6:16) indicates that fasting is normal and acceptable in the Christian life. He assumes His followers will fast on certain occasions, but He does not give a command or specify a particular time, place, or method. Because the validity of the Day of Atonement ceased when Jesus made the once-for-all sacrifice on the cross (Heb. 10:10), the single prescribed occasion for fasting has ceased to exist.
God is not so much interested in our fast as much as He is interested in us obeying His word. Through the prophets, God told the people of Israel that he wasn’t at all interested in their fasting if they didn’t bother to obey him. The way they treated the poor, the way they massacred justice—these actions spoke much louder about their spiritual devotion to God than their repeated days of fasting ever could.
Jesus says: “when we fast, we should not put on very sad, gloomy, dull faces… looking terrible… we should not disfigured our faces, or show off, or put up any act that make us look like we need the oohhh’s and the aahhh’s and all the ‘she’s on the mountain’ talk. By this act, we make our real faces, countenance “invisible” and our fasting ‘visible’ to all. When people notice our fast, that is the reward we get.
Action: It is public suffering: visibly sad and pitiful.
Motive: It is done for man’s praise.
Result: The reward is paid in full. You receive human praise.
By contrast, Jesus tells us in verse 17 how we should fast:
 But when you fast, put oil on your head and wash your face,  so that it will not be obvious to men that you are fasting, but only to your Father, who is unseen;
The point here is the opposite of letting everyone know you’re fasting. The oil he’s talking about here is just a regular part of hygiene in that day.
It means basically that when you fast, wash your face, comb your hair, dress well, apply some cosmetics if possible, look good, cheerful as always. Don’t try to make sure that everyone knows you’re fasting. Are you fasting to concentrate on God? Great! Then it’s really just between you and him. No one else needs to know. So don’t be obvious about it.
Does that mean that you must keep all fasting a secret?
I don’t think so. I don’t think this verse means that all fasting MUST be done in private. There are examples in the New Testament of groups fasting together. And as we saw earlier, Jesus doesn’t mean that there’s anything wrong with people knowing that you give, that you pray, or that you fast. The problem is when you do those things SO THAT people will know you’re doing them.
It’s not an issue of who knows about it or what they think about it. It’s all about your motive. Why did you do it? For people? Or for God?
So, even if you’re fasting with other people, keep your fasting a personal thing, just between you and God, and then your motives won’t be in question. God sees even what no one else can see.
and your Father, who sees what is done in secret, will reward you.
Just what is this reward?
The Bible doesn’t promise a specific reward for fasting. But I think we can make a pretty good guess. In the Bible, the thing that drives people to fast is their deep concern, their profound need for God to hear them and act. Perhaps that is the reward of fasting. If you are so intent on connecting with God that you skip a meal or two, then you will connect with God. It’s not because you were fasting. It’s because you were sincerely seeking God. And those who really seek him will find him.
So, Why are you fasting? Does your fast honor God? or does it only make you look and feel like a ‘spiritual sister or brother?’