7 'But evil-doers and sorcerers will wax worse and worse, deceiving and being deceived.' If therefore, like those expounders of dreams and false prophets who professed to give signs, these ignorant men being drunk, not with wine, but with their own wickedness, make a profession of priesthood, and glory in their threats, believe them not; but since we are tried, let us humble ourselves, not being drawn away by them. For so God warned His people by Moses, saying, 'If there shall rise up among you a prophet, or a dreamer of dreams, and shall give signs and tokens, and the sign or the token shall come to pass which he spoke to you, saying, Let us go and serve strange gods, which you have not known; you shall not hearken unto the words of that prophet or that dreamer of dreams.
For the Lord your God tries you, that He may know whether you will love the Lord your God with all your heart.' So we, when we are tried by these things, will not separate ourselves from the love of God. But let us now keep the feast, my beloved, not as introducing a day of suffering, but of joy in Christ, by Whom we are fed every day. Let us be mindful of Him Who was sacrificed in the days of the Passover; for we celebrate this, because Christ the Passover was sacrificed. He Who once brought His people out of Egypt, and has now abolished death, and him that had the power of death, that is the devil, will likewise now turn him to shame, and again grant aid to those who are troubled, and cry unto God day and night.
Source: Letters (New Advent)