Exodus 20:22 "You shall not build it of hewn stones"

This Negative Mitzvah describes the building of the altar on which sacrifices are offered.

The Hebrew word for sacrifice is "Korban", which comes from the word "Kerav", which means "to come close."

By presenting a sacrifice, a Jew becomes closer to HaShem, (see Introduction to Positive Mitzvah 39).

The altar on which sacrifices were offered was made out of stone.

The Torah forbids us to build the altar with any stone that was cut with a blade. An iron or metal blade is also a tool of warfare, used to make swords and knives and other instruments of death.

The Torah does not want the altar to be touched by such materials, because they represent the exact opposite of sacrifices which bring us close to HaShem and thus, extend our lives. Therefore, we must not build the altar with stone that has been cut with a blade.