THE HIDDEN DANGERS OF MORAL DECAY IN MODERN SOCIETY
First Reading: Genesis 6:5-8,7:1-5,10
Responsorial Psalm: Psalm 28(29):1-4,9-10
Gospel: Mark 8:14-21
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Yeast is a small but powerful substance that has been used for millennia in baking and fermentation. A tiny amount can transform an entire batch of dough, causing it to rise and expand. Because of this property, yeast has often been used symbolically to represent the hidden forces that influence a system, whether for good or evil. It spreads, permeates, and changes everything it touches. This symbolism is found in many cultures and religious traditions, including Judaism and Christianity, where yeast is often a metaphor for both the corruption of sin and the regenerative power of divine influence. In Jewish tradition, the term for yeast or leaven is שְׂאוֹר (se’or), which appears in the Torah primarily in the context of Passover. The Israelites were commanded to remove all “se’or” from their houses before celebrating the Feast of Unleavened Bread (Chag HaMatzot), commemorating their hasty departure from Egypt when they did not have time to let their dough rise. Yeast, in this context, came to symbolize the influence of sin, corruption, and impurity – something that must be purged in order to be spiritually clean. The prohibition of leavened bread during Passover was not just about diet but about removing the old influences of slavery, sin, and worldliness. In the Jewish mindset, leaven represented the slow but sure spread of moral decay, just as a little yeast eventually works through an entire batch of dough.
In the Greek New Testament, the word for yeast is ζύμη (zymē), and like in Jewish thought, it is often used metaphorically to describe both negative and positive influences. In many cases, “zymē” is associated with the corrupting influence of sin, hypocrisy, and false teaching. Jesus frequently warns against the “leaven of the Pharisees and the Sadducees”, referring to their hypocrisy and legalism, which distorted the true worship of God. At the same time, in a more positive light, “zymē” is used in Jesus’ parable of the Kingdom of Heaven in Matthew 13:33, where He describes the kingdom as yeast that a woman took and mixed into flour until it was completely leavened, showing how God’s rule begins small but gradually transforms everything. Yeast, therefore, represents an unseen but powerful force that has the ability to influence an entire system, either corrupting it or renewing it.
This concept is pertinent to understanding the First Reading (Genesis 6:5-8; 7:1-5,10), where the Lord sees that the wickedness of man was great upon the earth and that every inclination of the thoughts of his heart was only evil all the time. The passage describes a world completely permeated by corruption, much like a lump of dough entirely leavened by yeast. Just as a small amount of yeast spreads throughout the dough, so too had sin spread throughout humanity, corrupting everything. This was not a case of isolated evil but a systemic, all-consuming wickedness. The language used in Genesis 6:5 lays emphasis on the total depravity of the human condition – not just sinful actions, but the very inclinations (יֵצֶר yetzer) of the heart were continuously evil. The idea of “yetzer” in Hebrew refers to the deep, formative thoughts and desires that shape human actions. This corruption was not external but deeply rooted in the moral and spiritual depth of humanity.
Just as the Passover tradition required the removal of “se’or,” the Lord saw that the world itself needed to be purged. The flood became a means of cleansing, of removing the old yeast of sin that had permeated the human race. Noah and his family, like unleavened bread, were preserved as a pure remnant – a new beginning free from the corrupt influence of the world. The flood, then, is not just a story of destruction but of purification and renewal, an attempt to remove the old yeast and restart creation with a righteous foundation.
In Mark 8:14-21, Jesus picks up this imagery when He warns His disciples to “Beware of the yeast (zymē) of the Pharisees and of Herod.” The context of this statement is significant. The disciples were concerned because they had forgotten to bring bread, and when Jesus spoke of yeast, they misunderstood, thinking He was talking about physical bread. Jesus, aware of their confusion, rebukes them for their lack of understanding, saying, “Are your hearts hardened? Do you have eyes but fail to see, and ears but fail to hear?” (Mark 8:17-18). The phrase “hardened heart” (πεπωρωμένην καρδίαν – pepōrōmenēn kardian) is key—it connects directly to the corrupt heart of humanity in Genesis 6. Just as the people of Noah’s time were blind to their sin, the disciples were blind to the deeper meaning of Jesus’ words.
The yeast of the Pharisees represents hypocrisy, self-righteousness, and spiritual blindness. They had an outward appearance of religiosity, but their hearts were far from God. Their teachings, like yeast, spread corruption instead of truth, leading people away from genuine faith. The yeast of Herod represents worldly power, political corruption, and moral compromise. Herod was a man who, despite his knowledge of John the Baptist’s righteousness, still ordered his execution due to his own weakness and political entanglements. Both the Pharisees’ legalism and Herod’s worldliness were dangerous influences that could corrupt the disciples if they were not careful.
The theological significance of this passage is profound. Just as Genesis describes a world entirely leavened by sin, Jesus warns that false teachings and moral corruption continue to spread. The disciples, though physically close to Jesus, were still in danger of misunderstanding His message because their hearts were not yet fully transformed. Their failure to grasp what Jesus was saying shows that spiritual blindness is not just a problem for the Pharisees or for Herod, but for anyone who allows their heart to be hardened.
Several lessons emerge from this reflection. First, sin spreads like yeast – it may start small, but when unchecked, it permeates everything. The world before the flood was not immediately wicked; corruption spread gradually, affecting every part of human existence. This is true on both a personal and societal level. Small moral compromises can lead to greater corruption over time, whether in individuals, families, or entire civilizations. Second, purification is necessary for renewal. Just as Passover required the removal of yeast, and just as the flood washed away the corruption of Noah’s time, so too must believers actively seek to remove sin and false influences from their lives. This is not only about avoiding evil but about being intentional in seeking holiness and truth. Third, spiritual blindness is not just for unbelievers. The disciples, though they had witnessed Jesus’ miracles, still struggled to understand His teachings because their hearts were not fully open. This is a warning for all Christians—proximity to Christ does not guarantee understanding. We must remain vigilant and allow the Holy Spirit to enlighten our hearts. Finally, true transformation requires the right kind of yeast. While Jesus warns against the zymē of the Pharisees and Herod, He also speaks of the Kingdom of God as a good yeast (Matthew 13:33). The difference lies in what kind of influence we allow to shape us. If we are filled with the yeast of the world – compromise, hypocrisy, and self-reliance – we will be corrupted. But if we allow the yeast of the Kingdom – the Word of God, the grace of Christ, and the work of the Holy Spirit – to take root in us, then we will be transformed into the image of Christ.
The challenge for us today is to ask: what kind of yeast are we allowing into our lives? Are we being shaped by the leaven of sin or the leaven of grace? Are our hearts hardened like the Pharisees, or are we allowing God to soften and renew them? The choice remains before us, just as it did in Noah’s time, in Jesus’ time, and now in ours.
O that today you would listen to his VOICE, harden not your hearts! (Ps. 95:7)
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Shalom!
© Fr. Chinaka Justin Mbaeri, OSJ
Seminário Padre Pedro Magnone, São Paulo, Brazil
nozickcjoe@gmail.com / fadacjay@gmail.com
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