Athanasius of Alexandria

Since, as I said, there are many kinds of proclamations, let us listen to the trumpet blast of the prophet: “Blow a trumpet in Zion, consecrate a fast.” This is a warning trumpet, and it earnestly commands us that when we fast, we should do it in a holy manner, for God is holy and has pleasure in his holy people. Not everyone, however, who calls upon God honors him. Some defile him—although they don’t actually defile him: that’s impossible. But they do defile their own consciences concerning him. The apostle Paul tells us how it is that some people dishonor God: those who break the law dishonor God. So the prophet said, in order to point out those who pollute the fast, “Sanctify a fast.” Many people, though they go through the motions of a fast, are still polluted in their hearts because they do evil against their brothers and sisters or because they dare to cheat. And many, if nothing else, think more highly of themselves than of their neighbors, thereby committing a great offense.