A number of questions beg to be asked relating both to the Biblical portion of the week, as well as to the festival of Purim, which takes place both before (Ta'anit Esther, the fast of Esther, on Thursday) and immediately following the Sabbath of Tetzaveh (Saturday night and Sunday being the time when we read the Esther scroll and participate in all of the concomitant festivities and acts of loving kindness). Firstly, in the Biblical portion, why is there the emphasis on the various garments worn by the priests (from special vestments) and the High Priest (eight special vestments)? If "The Merciful One desires the heart," why such significance attached to external garb?
Secondly - and also concerning dress - a very difficult gloss of Rabbi Moshe Isserless (16th-century Ashkenazi decisor) relating to the laws of Purim says as follows: "Concerning the custom to wear costumes on Purim ('false faces' - partzufim) and for men to dress in women's clothing, there is no prohibition of this conduct. Their intent is merely for the sake of rejoicing." (Shulhan Arukh, Orah Haim, end of 696)
Why should Purim rejoicing outweigh the Biblical prohibition of men dressing in women's garb? Is masquerading - dressing like someone else - so central to the festivities of Purim?
In order to understand our sages, I believe it is necessary to go back to the very first Biblical personality who masqueraded - Forefather Jacob, who
Is masquerading - dressing like someone else - so central to the festivities of Purim?
dressed in the garb of his elder brother Esau (Gen 27: 15,16) in order to receive his father's blessing. What would cause Jacob, Biblically described as a "wholehearted individual, a studious tent dweller," (25:27) to don the aggressive and out-door garb of Esau? The truth is because Jacob wanted to become Esau, because Jacob's naive, introspective and serious personality had been rejected by his father in favor of the more extroverted, silver-tongued ("His entrapment was in his mouth," 25:28) and materialistic-minded Esau. Jacob wanted to become Esau because Jacob yearned for his father's love and embrace.

Is masquerading - dressing like someone else - so central to the festivities of Purim?

Jacob assumed a masquerade of the other - and, as happens so very often when someone masquerades - became the other, forsaking his true and essential self; Jacob forsook his pure, whole-hearted self, which was the truest expression of the Divine spark within him, and exchanged it for the outer garb of Esau. And so, the Jacob we watch in action for the more than two decades he spent with his Uncle Laban became an accomplished and aggressive businessman-herdsman, a materially successful cattleman who knew very well how to look out for "number one." The outer garb of Esau quickly replaced the inner voice of Jacob.
Perhaps, this is why our English word "personality" or "persona" comes from the Latin word for "mask"; many of us begin to continually wear the masks with which we masquerade, forsake our essential and truest selves for those whom we are pretending to be. And in this sense, Judaism would demand that external clothes do not necessarily make the man, but - very often - clothes fake the man. That's why the Hebrew begged, or "garment", comes from a root verb that means "to deceive," and the Hebrew me'il, which means "outer cloak," comes from a root verb that means "to embezzle."
From this perspective, we can better understand the characters of the Esther chronicle. Jews in exile, especially Jews who wish to be part of the Gentile class of their host country, often masquerade or assimilate, appearing to be as Gentile as possible. Hence, Esther, whose real Hebrew name was Hadassah (a myrtle branch, which blooms even in the desert) was the Gentile sobriquet - or external calling card, as is were. The name Esther is from the Persian goddess Astarte; Mordecai assumes the Persian Marduk.
Esther hides her true self - her Jewish identity - by not revealing her nation or her homeland (Esther 2:10). She spends twelve months in preparation for her nocturnal meeting with Ahashverosh, being externally perfumed and cosmeticized, so that her wholesome and pure body be "masked over" with all sorts of external fragrances. When she ascends to her lofty majestic position, she certainly does not dress as a Jewess would or reveal in any way her true identity. In like manner, "Mordecai told the courtiers that he was Jewish" (Esther 3:4) in order to explain his refusal to bow down to Haman. Obviously, he did not dress as a Jew, with phylacteries and ritual fringes; if he had, he wouldn't have had to inform them of his Jewish ancestry. Esther and Mordecai began as masquerading Persians in order to retain and maintain positions of influence within the Persian magisterial court.

The outer garb of the sacred ministers of the Temple must reflect their inner sanctity and mission.

Remember, however, that just as the masquerader puts on a false exterior facade, from which comes our English "face," the Hebrew word for face is panim, which literally means the internal (self), the true and interior being. Similarly, although exile, by its very nature, encourages assimilation and masquerade, nevertheless, the Hebrew word galut actually means to reveal or uncover. As the Bible guarantees, there will always come the moment of truth in which the assimilated Jew will return to his true self and re-establish his deepest roots in his homeland (Gen. 15:16, Ex 1:7,8; Lev.26:44,45). The masquerading Jew will either come to himself by throwing off his masquerade in a profound moment of repentance - as when Jacob succeeded in exorcizing the spirit and envy of Esau from within himself and returned "whole" to his ancestral home and homeland as Yisrael (he strove against beings divine and human, and he prevailed, Gen 32:29) - or as when an anti- Semite such as Haman forced a moment of truth upon Mordecai and Esther, and they decided in favor of their truest selves as Jews ready to risk their lives for their people and their G-d. At the end of the day, the masquerade falls to the ground and the true Jew must re-discover himself.
Now, we understand why so much attention is paid to the garb of the priests, with the emphasis on the twelve tribes and the statement on the High Priest's forehead turban, "Holy unto the Lord." The outer garb of the sacred ministers of the Temple must reflect their inner sanctity and mission; the very antithesis of the initial Purim masquerade, when neither Esther nor Mordechai appeared to be who they really were. And our commandment to drink on Purim reflects our faith that even under the influence of large quantities of wine drunk by the Persian aristocrats, the true Jew will emerge with words of Torah and praise to G-d, as did Mordecai and Esther.