With the approach of the holiest day of the year, an insight on the Yom Kippur service performed in the Temple by the High Priest: incense.
The incense offered up in the Temple was usually on the Inner Alter, which parallels the inner dimension of the heart–i.e., our Divine soul, which is constantly bound to its Divine source–and serves to reveal and intensify this bond. In contrast, the sacrifices offered up on the Outer Alter are designed to elevate the
outer dimension of the heart–our human/animal soul–to Divinity.
On Yom Kippur the essence was offered up in the Holy of Holies.
In this context, the burning of the incense on Yom Kippur in the Holy of Holies–the innermost part of the Sanctuary, more interior than even the Inner Alter–reflects the revelation on this day of the innermost dimension of the Divine soul itself. When this aspect of the Divine soul is revealed, our spiritual nature takes over our physicality, transforming us into quasi-angelic beings who have no need for food or drink. Thus, the various forms of “affliction” we are enjoined to observe on Yom Kippur, rather than punish us, are meant to express our metamorphosis into spiritual beings on this day.
As Rabbi Levi Yitzchak of Berditchev is quoted as saying regarding the injunctions to fast on Tisha b’Av (the anniversary of the destruction of the Temple) and Yom Kippur:
“There is no need for us to be commanded to fast on these days, for on Tisha B’Av, who can eat? And on Yom Kippur, who needs to eat?!”

–From: Kehot Chumash Vayikra