From the Teachings of the Lubavitcher Rebbe Rabbi Menachem Mendel Schneerson, Zt”l
The Torah portion of Tetzaveh contains the commandment to make a special altar for burning incense: "And you shall make an altar to burn incense upon." Our Sages explain that the Sanctuary and Holy Temple are symbolic of the Jewish soul; all of its components have a parallel in the spiritual make-up of the Jew, and reveal important lessons to be applied in our daily lives.
There were two different altars in the Sanctuary: an outer altar made of bronze, for animal sacrifices and meal-offerings, and an inner altar made of gold for burning incense. It was forbidden to offer anything except incense on the inner altar, and the person burning the incense had to do so alone, without anyone else present in the chamber.
A Burning Love for G-d
In general, the altar is symbolic of the heart and the Jew's innate, burning love for G-d. More specifically, however, the outer and inner altars of the Sanctuary symbolize two different levels of this love, i.e., its external and internal aspects, as well as two different ways of approaching our Divine service.
For example, there are many things a Jew must do which require only the "outer" aspect of the heart. Other pursuits, however, should be approached with the utmost enthusiasm and full inner powers of the soul.
To illustrate: A Jew is obligated to eat, drink and sleep, and attend to the physical health of the body. These activities, however, should not be done for personal pleasure, but in a manner of "All of your deeds should be for the sake of Heaven," and even the higher level of "Know Him in all your ways."
Only the “External” Aspects of His Heart
In the same way the Sanctuary's outer altar was reserved for offering "limbs" and "fats," a Jew should approach the fulfillment of his physical needs with only the "external" aspects of his heart, i.e., without undue enthusiasm, as if fulfilling an obligation.
By contrast, the "internal" aspects of the heart should be reserved for the pure service of G-d, for learning Torah and prayer. A Jew's true enthusiasm and inner vitality should be channeled into holy pursuits, in the same way the incense on the inner altar rose completely upward to G-d, without leaving a residue or remain.
Acting Solely for the Sake of G-d
When offering the incense, the kohen (priest) had to be alone in the chamber. Symbolically, this means that when it comes to matters of holiness a Jew must act solely for the sake of G-d, humbly and without trying to attract attention: only the individual and G-d need to know about it. When a Jew serves G-d with pure intention, he merits that the Divine Presence will rest of the work of his hands.
Reprinted from Parshat Tetzaveh 5762/2002 edition of L’Chaim, a publication of the Lubavitcher Youth Organization. Adapted from Volumes 1 and 6 of Likutei Sichot.