The bond of faith
Faith is when the lower levels wish to bind with the upper levels.
This term is used throughout the Zohar. It represents the bond created between Zeir Anpin and Malchut, and Yessod is the element that binds the upper levels with Malchut.
The Ketoret is also a tool for the bond of faith to unify upper and lower. Because of that, the Ketoret was served on the Golden Altar that was facing the Holy of Holies, not outside the temple.
To bind with the spiritual level, we need faith to connect to the spiritual levels with the ‘Bond of Faith.’ Then we can see beyond the material level.

Synonyms:
קשר האמונה