The contrast is clear in the verse itself: “old yeast” stands for corrosive moral qualities—Paul names “malice and wickedness”—while “unleavened bread” stands for fitting qualities—“sincerity and truth.” The point is a mismatch: a community cannot meaningfully celebrate what God has done while keeping the “ingredients” of the old way of life at the center of its shared life.

Where interpretation differs (only where needed)

Is “keep the feast” literal or metaphorical? Some readers take Paul to be referring to an actual religious festival meal (often connected to Passover language in the surrounding context), meaning that the community’s practice of worship and communal meals should align with moral seriousness. Others take “keep the feast” as a metaphor for the whole shape of life as a community—ongoing celebration expressed in a consistent moral character.

What does “truth” emphasize? Some read “truth” mainly as honesty and transparency in relationships (the opposite of concealment or hypocrisy). Others read it more as faithfulness to God’s message about Jesus—living in line with what the community confesses and teaches.

Why the disagreement exists

Paul uses compressed imagery rather than step-by-step explanation. “Feast,” “leaven,” and “unleavened bread” can refer both to actual practices around meals and to moral influence. Also, the paired virtues “sincerity and truth” can naturally describe both relational integrity and alignment with God’s revealed message.

What this passage clearly contributes

This verse explicitly links communal celebration with moral consistency. It portrays wrongdoing as something that spreads through a group like yeast through dough, and it identifies “malice and wickedness” as incompatible with the community’s identity. It also names “sincerity and truth” as the fitting character of the community’s shared life. The passage contributes a theological claim about coherence: what the community honors in its shared worship and identity should be reflected in the “ingredients” of its communal behavior (an inference grounded in Paul’s contrast and his “therefore” conclusion). See also 1 Corinthians 5:6 and 1 Corinthians 5:7.

unleavened bread (azymois)