God demands what and how offerings should be given to him – e.g., “without defect” and “be accepted before the LORD” (vv. 1-3). Also, God demands offering “by fire of a soothing aroma to the LORD” (vv. 9, 13 and 17), which becomes the repeated pattern in Leviticus.
Just like the previous chapter on offering without defect and soothing aroma, God demands the offering must not contain any leaven (v. 11), which signifies contamination. Hence, God demands purity or pure offering. All that is to say, the offering requires perfect and sinless to be qualified to function and serve as God’s acceptable offering. This is a preview of the coming sacrifice that is perfect and sinless that God will accept, namely his son Jesus!
Since chapter 1 various offerings are stated: from burnt offerings (chapter 1), grain offerings (chapter 2), and now the peace offerings. Just like the previous chapters here the emphasis once again is on the offering that is “without defect” (v. 6). Hence, God demands what and how he is to be offered and be served. Again Jesus fulfills all this.
The word “atonement” is the key word. It is repeated (vv. 26, 31, 35). The obvious implication is that sin needs to be atoned. Sin should not be left unchecked, untreated, disregarded, or belittled. Rather, it needs to be atoned. And God mandates what and how to atone sins (though it is not permanent and needs perpetual sacrifices) until Jesus later accomplishes what no man can accomplish.