Upon arriving from the Babylonian exile, the people who returned specifically alongside Ezra chose to offer a unique series of sacrifices [רש"י]. These offerings were not intended solely for the returnees themselves. Instead, they were brought on behalf of all Israel, serving as a representation of the entire nation [מצודת דוד].
To reflect this national representation, they offered twelve bulls, matching the number of Israel's ancestral tribes [אבן עזרא, ביאור שטיינזלץ]. Alongside the bulls, they also offered twelve male goats as sin offerings [רב סעדיה גאון, מצודת ציון, ביאור שטיינזלץ]. This specific combination of twelve bulls and twelve goats was meant to hint at a process of purification from the sin of idolatry. According to Jewish law, if the public is led to commit idolatry due to an erroneous ruling, they must bring a bull and a goat for each tribe. Even though the returnees were not strictly obligated to bring these sacrifices, they offered them to awaken the people and emphasize their complete purification from past sins [רלב"ג].
In addition to these, dozens of rams and lambs were offered. Some suggest that the specific number of ninety-six rams was deliberate, as it equals twelve multiplied by eight, maintaining the connection to the tribes [ביאור שטיינזלץ]. Conversely, another approach maintains that the numbers of the ninety-six rams and seventy-seven lambs hold no special symbolic meaning. Rather, they simply reflect the quantity of animals the people could afford to sacrifice based on their financial abilities at the time [אבן עזרא].
The conclusion of these offerings featured a dramatic deviation from standard Jewish law. The primary approach among commentators is that all of these special sacrifices, including the sin offerings, were burned completely on the altar. Unlike standard practice, where the priests would eat a portion of the sin offering, everything was entirely consumed by fire [מצודת דוד, ביאור שטיינזלץ]. Commentators agree that this deviation was a temporary, exceptional ruling established exclusively for that unique moment in time [רש"י, מצודת דוד, מלבי"ם]. However, a dissenting view argues that the complete burning applied to all the sacrifices except for the sin offerings, which were handled normally and not completely burned [רלב"ג].
Beyond the legal mechanics of the sacrifices being entirely consumed by fire, there is a deeper conceptual meaning tied to the event. The concept of an offering going up in smoke hints at a need for atonement regarding the thoughts that "go up" or arise in a person's heart. Many of the returnees did not leave Babylon out of a full, willing desire; instead, they felt almost forced to make the journey by Ezra. The completely burned offering served to atone for this hesitation and the imperfection of their willingness to return [חומת אנך].