There were two mizbeichos, altars, in the Mishkan and the Beis HaMikdash. They were the mizbeiach hazahav and mizbeiach hanechoshes, the golden altar and the copper altar. The golden altar was used for offering incense, while the copper one was used for regular offerings.

Details of the copper altar are discussed in the Torah portion of Terumah, while the golden altar is described in the portion of Tetzaveh.

The Mishnah informs us in Tractate Chagigah1 that both the golden and copper altars were immune to ritual impurity. R. Eliezer says the reason for this is that the altars are likened to earth, and earth is not subject to ritual impurity. The Sages, however, explain that they were not subject to ritual impurity because the altars were merely covered with gold or copper. As such, their covering was nullified before their interior, which was composed of material not subject to ritual impurity.

In terms of our personal spiritual service, the teaching of the Mishnah is as follows: In its spiritual sense, the Tabernacle and all its vessels are found within every Jew. Man himself is likened to the Mishkan, while his faculties of intellect, emotion, etc., are similar to its vessels.

These vessels can become defiled and spiritually impure when a person acts contrary to G‑d’s will.

Once this occurs, the vessels must be purified so that they may continue to be used in the service of man’s personal Tabernacle. For every Jew is considered G‑d’s Holy Temple, and the Temple and its vessels must be spiritually pure.

People fall into two categories: either they are wealthy or they are not. This wealth may be either spiritual or material. Of he who is wealthy, it is said that “everything he possesses is of gold,”2 while of he who is not wealthy, it is said that “all his coins are copper.”3

Every Jew, however, even one whose spiritual status is merely “copper,” is whole with regard to that quintessential part of him that makes him what he is, a Jew. That part always desires to fulfill G‑d’s will. As stated in HaYom Yom: :4 “A Jew neither desires, nor is capable, of sundering himself from G‑dliness.”

A Jew’s inability to separate himself from G‑dliness, and his readiness to sacrifice himself and his animalistic desires for G‑d, is termed mizbeiach, an altar upon which the individual sacrifices his individuality, ego and desires. The above-mentioned Mishnah thus informs us that, whatever a Jew’s level, be he of “gold” or “copper,” his Jewish essence is not subject to ritual impurity.

According to R. Eliezer, the reason for this is because the innermost desire of every Jew is to fulfill G‑d’s will to the exclusion of all else. This is because a Jew’s essence possesses a humility before G‑d that causes him to be likened to earth, which permits itself to be trodden upon by all.

The other Sages, however, feel it is too much to expect that we will be able to see the essence of the Jew to the exclusion of all external characteristics. They therefore state that the reason Jews are not subject to impurity is because, although externally some Jews may be led astray by their wealth (their “gold”) or their poverty (their “copper”), their essence — their “altar” — is not subject to spiritual impurity.

The reason for this is that the rich man’s gold as well as the poor man’s copper are merely external coverings; the individual’s core is entirely pure. So indomitable is this internal holiness that eventually, every external impurity is nullified before it.

Based on Likkutei Sichos, Vol. III, pp. 910-913