In Jewish history, there were three stages to how sacrifices were brought:

Until the time of the Giving of the Torah, there was the bama ("platform") on which every Jew could offer up his own individual sacrifice as he saw fit, when he saw fit. For this, the person bringing the sacrifices did not need to be a kohen, nor was he limited by special priestly laws.

...only the kohanim could offer up sacrifices.

Second, there was the Mishkan ("Tabernacle") which the Jews built in the desert, and which traveled with them on their wonderings, and also came with them into the land of Israel. Here, only the kohanim could offer up sacrifices. However, whenever the altar of the Tabernacle was inoperative for some reason, it was permissible for individuals to offer sacrifices on their own bama.

Third, there was the Beit HaMikdash ("the Holy Temple"). When it was built, individual sacrifices became completely forbidden because there was now a permanent altar with kohanim — and only kohanim – offering up sacrifices at all times.

During the time when anyone could offer sacrifices on the bama, there was no special limitation placed on those bringing those sacrifices. It was only the kohanim who were limited by special laws when they did so. (That is, they could not associate with the dead, marry divorced women, etc.)

What do these limitations have to do with the added holiness of the kohanim?

Shem miShmuel explains that the three stages of offering sacrifices correspond to three aspects of the Jew:

  • Intellect (neshama or divine soul)
  • Animating soul (nefesh or animal soul)
  • Body

The intellect, being individual and independent, corresponds to the bama, on which every individual Jew could offer up his own sacrifices. No Jew thinks like another Jew – we all have our own opinions and approaches. The individual bama enabled every Jew to elevate his own neshama or divine soul and connect it with its source Above, thereby drawing down prophecy and holiness into the world.

The Tabernacle had the added dimension that it could also elevate the nefesh – the enlivening soul or animal soul. The main materials of the Tabernacle were animal skins and wood, which express life and growth. The nefesh is the source of life and growth, and this is why it corresponds with the Jewish animal soul, which enlivens and enables the Jew to grow.

...the Holy Temple, made mostly of stone, has the ability to elevate the Jewish body.

And finally, the Holy Temple, made mostly of stone, has the ability to elevate the Jewish body. The physical is the most difficult component of the person to elevate, but the sacrifices of the Temple had the ability to elevate even the physical body.

And why could only the kohen offer sacrifices in the Temple?

The kohen’s task was to bring union. It was his job to join opposites – heaven and earth. By offering the sacrifices and performing the other services of the Temple, the kohen caused holiness to penetrate the physical universe and make itself known to humanity. Since his job was to create oneness and unity, he could not tolerate the opposite. He could not tolerate the presence of separation, which is called tumah ("impurity").

The only place in which the sacrifices created union was in the Temple. Only there did the sacrifices create union between G‑d and the nefesh, G‑d and the body. And therefore, only the kohanim could offer sacrifices in the holy Temple.

However, every soul (neshama) feels that its rightful place is with the Creator. Every spiritual intellect wishes to separate itself from the body and cleave to G‑d. The bama represented the spiritual intellect of the individual, and therefore it didn’t matter who performed the sacrificial service – individual Jew or kohen. Since the purpose was to cleave the soul to G‑d, it didn’t matter who performed the sacrifices. It was only the Temple, which joined the upper worlds with the lower worlds, that required the extra sanctity of the kohen.