The answer is: Feast of Weeks

Lev 23:17 - The two loaves waved can be seen as a symbol of the church being made from two groups, the Jews and the Gentiles. The leaven represents the sin within them.

The Feast of Weeks, known as Shavuot in the Jewish tradition, is a fascinating celebration rich with layers of meaning. This feast marks the end of the grain harvest, typically embodying gratitude for the bounty of the earth. But what really makes this observance unique is the inclusion of leaven in the offering—contrary to the general practice during Passover, where leaven (or yeasted bread) is utterly forbidden.

Here's where the symbolism kicks in! Those two loaves, made with leaven, can be interpreted as representing the complexities of humanity—both Jews and Gentiles as part of a unified community, rich in diversity yet flawed. Unlike during Passover, where unleavened bread symbolizes purity and redemption from sin, the leavened loaves at Shavuot sense humanity's imperfections, signifying that, despite our flaws, we are brought together.

In biblical lore, leaven takes on different meanings. Sometimes it symbolizes moral corruption, such as in Jesus’ warning against the leaven of the Pharisees. Interestingly, it also connotes growth—like yeast that transforms dough into fluffy bread! This duality shows that imperfection can not only exist alongside divinity but often plays a key part in collective growth and understanding.

The mention of Shavuot also recalls the giving of the Torah, linking food and the written word, and suggesting that just as bread nourishes the body, teachings nourish the spirit. This melding of bread and belief fosters a deeper appreciation for how all humans share a common journey through faith, embodying growth in unity among imperfections.