http://revach.net/article.php?id=4463

Section: Parshas HaShavua   Category: Quick Vort
Parshas Vayikra: Chidushei HaRim - What Is It About Korbanos That Smell So Good?
"Rei'ach Nichoach Lashem" is the often used phrasing in the Chumash to express Hashem's satisfaction with a Korban.  Does it actually smell good?  Does Hashem care?

The Chidushei HaRim explains that odors and fragrances are sensed even when you are still far away from the object emanating the smell.  Anything that you can sense before actually approaching is called smell.  We can smell something fishy before we actually know what is wrong.

A Korban is supposed to be a Mivaser Tov, and bring in good tidings.  The Korban is the sign of the improved ways of the regretful Baal HaKorban.  He has sacrificed his sins and promises to mend his ways.  This is the essence of a Korban.  This Korban is Rei'ach Nichoach and great satisfaction to Hashem, as Hashem smells the return of one of his lost children.