The prophets frequently emphasize that religious rituals, specifically the sacrificial service, lose all their value when they are disconnected from basic morality and justice. God expresses a total rejection of the offerings the people bring, despite these rituals being a strict obligation.
Even though the people bring burnt offerings and grain offerings, God declares that He will not accept them. This rejection is particularly harsh because the people were commanded to bring these offerings during the holidays, and the burnt offering was specifically designed to achieve atonement for certain sins. Despite their obligatory nature and their purpose of seeking forgiveness, God completely refuses to accept them [מלבי״ם]. This message aligns closely with the rebukes of other prophets, who strongly opposed the bringing of many sacrifices when they were not backed by the proper internal intention [רד״ק, מלבי״ם].
The rejection extends even further to the peace offerings. Since God rejects the mandatory offerings meant for atonement, He certainly refuses to even look at the voluntary peace offerings, which are traditionally brought out of joy [מלבי״ם]. While these are generally understood as the actual animal sacrifices [אבן עזרא, רד״ק, מצודת ציון], another perspective suggests that God is rejecting the very money paid to purchase these animals [ביאור שטיינזלץ].
The animals brought for these peace offerings are described as exceptionally plump and high-quality [רש״י, רד״ק, מצודת ציון]. Regarding the exact nature of these premium animals, there are differing views. Some suggest they belong to a distinct species of large cattle, similar to an ox, which has specific dietary laws permitting its fat. However, the primary approach among commentators rejects this idea, concluding that it is not a unique species at all. Rather, it simply refers to regular cattle that have gone through a special and careful fattening process [אבן עזרא].