The first place Scripture talks about the pleasing aroma is Genesis 8:21. Noah offers a sacrifice and the Lord smells the pleasing aroma and makes a promise never to again curse the ground because of man.
But over and over again in Exodus, Leviticus, and Numbers the "pleasing aroma" comes up. The daily offerings, monthly offerings, each feast and festival, all have sacrifices that are burnt as a food offering, a pleasing aroma to the Lord. And it's not just the smell of barbecue; the pleasing aroma is also tied to grain offerings. (Maybe it's not really about the smell but what it represents?) Honestly, the repetition here feels a little monotonous at first and then I remember how many times I have to hear things before I really take notice. (Like... LOTS!)
Finally, however, we make it to Ezekiel and things get all dark. The Israelites were offering their pleasing aromas to idols instead of God. Interesting that their offerings were not equated the burnt animals, but that the essence of the offering was actually the pleasing aroma.
Then Ezekiel 20:41 uses the phrase as a simile to describe the restoration of Israel saying, "As a pleasing aroma I will accept you, when I bring you out from the peoples and gather you out of the countries where you have been scattered. And I will manifest my holiness among you in the sight of the nations." Here the people themselves will be accepted in the same way as the Lord accepts the pleasing aroma of the sacrifice. Nice, right? How does that even work?
Shazaam! The New Testament explains!
2 Corinthians 2:14-16. "But thanks be to God, who in Christ always leads us in triumphal procession, and through us spreads the fragrance of the knowledge of him everywhere. For we are the aroma of Christ to God among those who are being saved and among those who are perishing, to one a fragrance from death to death, to the other a fragrance from life to life. Who is sufficient for these things?"
1. The aroma is still to God.
2. It's not always pleasing to people (for some it's life for others death).
3. The aroma is still of the sacrifice: Christ Jesus!
4. It is the aroma of his sacrifice that we carry with us that grants us welcome to God, thus fulfilling Ezekiel 20:41.
There are other verses that expand on this related to the fragrant offering of Christ, but this popped out to me with just the word "aroma".