God's altar demands absolute purity and simplicity, rejecting any elements that express pride, material lust, or idolatrous customs. The prohibition against leavening is sweeping and absolute. It applies to all meal offerings without exception, including those that are entirely burned and not eaten at all [תורה תמימה, מלבי״ם], as well as communal offerings like the showbread and libations. This strict standard governs every stage of preparation, from kneading and shaping to baking, ensuring that even the remnants eaten by the priests are never leavened [הירש, מלבי״ם].
The restriction carefully distinguishes between the fermenting agent itself, such as yeast or sourdough starter, and the actual dough that has risen as a result of that fermentation [מלבי״ם, ביאור יש״ר]. Similarly, the prohibition against honey extends beyond bee honey to include any sweet fruit nectar, such as the syrup of dates or figs. This is evident because the subsequent allowance for first fruits applies to produce harvested from trees rather than from bees [רש״י, רשב״ם, רא״ם, אבן עזרא, הירש, הופמן]. The restriction is exceedingly severe, forbidding even the most minute quantity or a mixture containing a trace of these substances from being burned on the altar [רמב״ן, תורה תמימה, פרדס יוסף].
The primary approach among commentators is that this prohibition historically served to distance the Israelites from pagan practices, as idolaters routinely offered leavened bread and mixed honey into their sacrifices [רמב״ן, רבנו בחיי, תולדות יצחק, טור]. On a moral level, these ingredients symbolize negative traits that must be eradicated when standing before God. The fermenting agent, which inflates the dough, represents the evil inclination, pride, and self-aggrandizement. Conversely, honey symbolizes the pursuit of physical pleasures and material desires, which may seem sweet initially but ultimately prove harmful. An offering must be brought with pure intentions, devoid of an inflated ego or the sweetening of ulterior motives [כלי יקר, בעל הטורים, שפתי כהן]. Furthermore, fermentation represents artificial human manipulation of the natural world, whereas the sanctuary demands a return to the pristine simplicity of creation as given by the Creator [העמק דבר]. Mystically, substances that have been altered from their natural, balanced state evoke the attribute of strict justice and are therefore kept away from the altar of mercy [רבנו בחיי, תולדות יצחק].
From a national perspective, unleavened bread reflects a heart subjugated to God and the recognition of divine grace. In contrast, leavened bread symbolizes political independence and self-reliance, while honey represents the natural wealth and abundance of the land. By excluding these from the altar, the Israelites are reminded that national sovereignty and prosperity are not independent human achievements to be offered back to God as if they were personal possessions [הירש]. Practically, the fermenting process creates air pockets in the dough. This would compromise the exact, solid measure required when the priest takes a handful to burn, as that portion must be entirely whole and free of voids [טור]. Additionally, neither leaven nor honey absorbs salt properly, and since all sacrifices require salt, they are rendered unfit for the altar [דעת זקנים].
Despite the absolute ban on burning these materials on the altar, they are not entirely rejected from the sanctuary. They are permitted as first offerings, such as the leavened loaves brought on the festival of Shavuot and the sweet first fruits. These elements symbolize practical life, human drive, and earthly abundance, all of which are essential for existence and can be elevated in holiness. However, their role is strictly limited to being waved and consumed by the priests, and they are never to be placed directly on the fire of the altar [כלי יקר, הירש, הופמן].