In this week's parsha, Moses receives instructions regarding the composition of the incense that was to be offered to God twice a day. In Sefer Breishit, we find another instance in which the sense of smell teaches us a similar lesson regarding repentance. When Joseph is sold to the Ishmaelites, he joins a caravan that is carrying spices, balsam and lotus to Egypt. The answer lies in the nature of the sense of smell. More than any other sense, recognizing a certain aroma can take one back to an earlier experience in which the same aroma was present.
Smells leave a lasting impression in a manner unequaled by any of the other senses.
In the case of Joseph's brothers, during their journey to Egypt, they were constantly reminded of the sinful act they committed against Joseph. We represent ourselves not as perfect beings, but as occasional sinners who are in need of divine assistance. We find that, in Judaism, it is not enough to have good intentions for the future. The often-overlooked chelbena ingredient, mentioned in this week's parsha, is a reminder of this principle.