Construction of the Altar

Why no stones hewn of iron in making altars

Shalom!

Thank you for your question!

You are correct, that metal/iron was not permitted to be used in the construction of the altar. As the Torah says, “When you build Me an altar, do not make it from cut stones. Raising your sword on (the altar) will desecrate it” (Exodus 20:22)

If metal tools were used in the construction of the altar then the altar is disqualified and may not be used. The reason for this, as it is explained, that the altar is an instrument of peace and iron tools are instruments of war and bloodshed. Anything affiliated with war and bloodshed are not compatible with things associated with blessing and life, and by extension serving G-d. Indeed, based on the altar precedent, there is a general preference to avoid metals in the performance of certain mitzvot.

In addition to the ban on constructing the alter with metal, twice a year the altar was whitewashed and even the paintbrushes that were used for this could not contain any metal.

In the words of the Mishna:

The stones both of the ramp and of the altar were taken from the valley of Beit Kerem. They dug into virgin soil and brought from there whole stones on which no iron had been lifted, since iron disqualifies by mere touch, though a scratch made by anything could disqualify…They were whitewashed twice a year… The plaster was not laid on with a trowel of iron, for fear that it might touch and disqualify. Since iron was created to shorten man's days and the altar was created to prolong man's days, and it is not right therefore that that which shortens [life] should be lifted against that which prolongs [life].

We hope that explains it!

Middos 3:4