“Moreover, when you fast, do not be like the hypocrites, with a sad countenance.
For they disfigure their faces that they may appear to men to be fasting.
Assuredly, I say to you, they have their reward.”
(Mt 6:16)

You disfigure your face when your interior disposition is concealed by a sham external appearance,
hidden by a lie as if covered under a veil.
He is a hypocrite who assumes in the theater an identity that is not his own.
Though a slave, he often assumes the identity of a master; though a private citizen, that of an emperor.
Similarly, in this life many act as if they were playing themselves on a stage,
carrying in their heart one thing but superficially displaying something else to people.
So then, do not disfigure your face. Appear such as you are.
St. Basil, On Fasting