Shared ground
Matthew 6:16–18 treats fasting as a real practice Jesus expects will happen (“when you fast”), but it targets how it is done. The main contrast is between fasting aimed at human attention and fasting aimed at God. Some people intentionally adopt a miserable look and alter their face so others will identify them as fasting. Jesus says that public recognition is the only “reward” they get.
Jesus’ alternative is deliberately ordinary: normal grooming (“anoint your head and wash your face”) so that the fast is not noticeable. The passage centers on “your Father” as the true audience. God is described as present “in secret” and as the one who “sees in secret,” in contrast to the social gaze.
Where interpretation differs
What “reward” means. Some read “reward” mainly as the social payoff: human admiration is the whole payment for the showy fast. Others think Jesus also points to a real divine response—God’s favorable regard or action—without specifying what form it takes.
Whether Jesus rules out all public fasting. Some think the teaching effectively requires fasting to be private in normal cases. Others think the target is not public settings as such, but the deliberate signaling (“so that they may be seen”), leaving room for fasting that becomes known for unavoidable reasons.
How literal the grooming instructions are. Some take the words about anointing and washing as straightforward instructions for appearance during a fast. Others take them as vivid examples standing for a broader idea: maintain a normal presentation so fasting is not used to manage reputation.
Why the disagreement exists
The passage uses everyday actions (face, washing, anointing) to make a moral point about visibility, so readers differ on whether the details are meant as fixed rules or as representative illustrations. Also, “reward” is stated without details, which leaves room for readers to connect it either to immediate social dynamics or to God’s later response (or both). Finally, “in secret” can be heard as a location (“private”) or as an audience focus (“hidden from people, known to God”).
What this passage clearly contributes
The text clearly frames fasting as a practice that can be corrupted by the desire to be noticed. It draws a sharp line between appearing religious and being oriented toward God. It also reinforces a wider theme in this part of Matthew 6: God is not impressed by managed appearances, and God’s attention is directed toward what is hidden. The point is less about fasting techniques and more about the intended audience of religious devotion (people vs. the Father who sees what others cannot).