When the people of Israel were in the desert upon the exodus from Egypt, they were instructed upon entering the Promised Land to give of a dough offering every time they made bread. These verses were the source of the system of tithing bread. The Kohanim — priests — did not own or work land; the rest of the people gave them tithes from their own produce so that they could be sustained while fulfilling their priestly tasks in the Holy Temple. Every time bread was made, a part of the dough was separated to be baked for the priests. This part was called ‘challah’ and the term now also refers to the loaves we eat today.
The destruction of the Temple meant the cessation of tithing; it became transmuted into the current practice of hafrashat challah, in which a portion of challah is still taken and separated, but instead of being given to kohanim, it is burned and rendered inedible, commemorating this interdependence between the Israelites and the kohanim.
There is a famous verse in the Torah that states: “Make Me a Mikdash (sanctuary) and I will dwell among them.” The Sages point out that the verse does not say “in it,” but rather, “among them,” which they interpret to mean that if you make space for it, then the Divine Presence can and will dwell within each Jew. By extension, every Jewish home has the potential to be a microcosm of the Sanctuary, and the various labors that we perform within our homes are comparable to those of a kohen working in the Holy Temple. It may seem that the kohen was doing work of a purely material nature, but in actuality all of his tasks were carried out with the intention of fulfilling the will of God; so can it be in our homes.