the Prophet Isaiah:
Yet they seek Me daily, and delight to know My ways, as a nation that did righteousness, and forsook not the ordinance of their God. They ask of Me the ordinances of justice; they take delight in approaching to God. Wherefore have we fasted, say they, and Thou seest not? Wherefore have we afflicted our soul, and Thou takest no knowledge? Behold, in the day of your fast ye find pleasure, and exact all your labours. Behold, ye fast for strife and debate, and to smite with the fist of wickedness. Ye shall not fast as ye do this day, to make your voice to be heard on high. Is it such a fast that I have chosen? A day for a man to afflict his soul? Is it to bow down his head as a bulrush, and to spread sackcloth and ashes under him? Wilt thou call this a fast, and an acceptable day to the Lord? (Is. 58:2–5).
That is, ”They sought Me daily and desired to learn the wisdom of My providence, as if they were some righteous people which kept the ordinances of God. And they say: ‘Lord, why did You not see us when we fasted? Why do You not want to know that we underwent such hardship?’” And God answers: “I do not hear you. For whenever you fast, you continue to do your wicked will. I do not want such a fast, nor such hardship. And even if you were to spread sackcloth and ashes on the ground beneath you like a bed, still I would not accept such a fast.”
However, when labors and virtues are done according to the will of God, then are they acceptable to Him and beneficial. The will of God is that we do whatever our Lord commands, Who says to us: “Whoso eateth My flesh, and drinketh My blood, hath eternal life” (Jn. 6:54). This is not only a commandment, but the chief of all of the commandments, for it is constitutive of and perfects the rest of the commandments.