Isaiah 58:5

“It is to be a sabbath of solemn rest for you, that you may humble your souls; it is a perpetual statute.

Then I called for a fast there at the river of Ahava, that we might humble ourselves before our God to seek from Him a direct journey for us, our little ones, and all our possessions.

“Speak to all the people of the land and to the priests, saying, ‘When you fasted and mourned in the fifth and seventh months these seventy years, was it actually for Me that you fasted?

“Now whenever you fast, do not put on a gloomy face as the hypocrites do, for they neglect their appearance so that they will be noticed by men when they are fasting. Truly I say to you, they have their reward in full.