Spiritual and Ethical Issues in the Sh'mot Stories
"In the Desert of Sinai" 
All the actions of people require preparation and from these preparations we are able to deduce the reliability, sincerity and longevity of actions. So too, in spiritual and religious actions, the preparations determine the spiritual value of these actions. "When we hire a craftsman we pay him not only for the time of his labor but also for the preparation of his tools, skills and expertise; so too our mitzvot and avoda are according to the preparation. One whose avoda is casual, whatever comes to hand or to mind, or simply to satisfy expectations of others, does nothing except prepare a present for Eisav; 'Yaakov took whatever came to hand - a present for his brother Eisav' (B'reishit 32:14)" (Menachem Mendel of Kotsk). The structure of our daily prayers in preparation for the obligation to recite Sh'ma and the Sh'moneh Esrei are a simple and everyday example of the way all our mitzvot need to be done. R' Simcha Bunem of Physhischa taught that only the mitzva of tzedaka is exempt from this requirement of preparation, since the poor could die while we prepare ourselves.
In our story, the preparation took three forms, in space, in time and physical sanctification and purification:
"In the third month after leaving Egypt, they journeyed from Refidim and encamped before the mountain, in the desert of Sinai" (Sh'mot 19:1-2). "Everywhere else it is written, 'they journeyed and they camped', they journeyed in strife and they camped in strife, but here encamped is written in the singular" (Mechilta). "Refidim has the letters of PIRUD, a sign of the divisions that existed in Israel then, so they had to journey away from Refidim and camp [singular] before Sinai, like one person with one heart (Kli Yakar). This unity is a necessary requirement for receiving Torah that represents not the individual's way to G-d but a political entity that is more than the sum-total of the individuals in it, the soul of a nation-religion. "That is why the Torah was not given to Adam or to No'ach, even though G-d made a covenant with them and gave them the 7 Noachide laws; these were natural requirements for society. Neither was the Torah given to Avraham, Yitschak nor Yaakov; even though they kept the whole Torah - that was something they achieved through their own religiosity and spirituality not something commanded them. Moshe gave Torah to Am Yisrael as a command from G-d" (Abarbanel). Indeed, it is uniquely Jewish that, "Greater is he who is commanded and observes than he who observes without being commanded" (Sanhedrin 31a, Baba Kama 38a); the former is obedience to an external truth whereas the latter is essentially the product of one's own desires and wisdom.
Why was it necessary to give the Torah in the ownerless space of the desert rather than in the settled land? After all, that land was the chosen site for the performance of all the commandments: Tefillin, Talmud Torah and Mezuza that are mentioned in connection with longevity in the land, though they are not mitzvot T'LUYOT BA'ARETZ, in essence they too were intended to be observed there; when in exile we should observe them so that they will not be strange when we return (Rashi, Devarim 11:21). The Torah was given in the desert, rather than in Eretz Yisrael, so that the nations should not say that they have no share in it since it belongs only to the people in that land; rather all who so desire may come and share in it (Mechilta).
There was also a preparation in time, the three month period from the Exodus to arriving at Sinai. "Why wait three months? Said Rabbi Chiya the Elder: 'A convert, a captive [Y'fat To'ar] and a freed slave may not marry or be engaged before a 3-month period has elapsed. Israel were GEIRIM - 'gerim hayitem im Hashem' (Vayikra 19:34), captives (Yeshayahu 14:3-4), and freed slaves, since G-d took us from being slaves to Par'o. After He waited three months, G-d said, 'Now I can give them My Torah (Tanchuma). "These months, Nissan, Iyar, Sivan, during which we left Egypt and traveled to Sinai to receive Torah on Shavuot, bear zodiac signs indicative of the different types of spiritual avoda that were achieved then; what is achieved spiritually by the individual by his own efforts and creativity, as compared to that achieved through the attachment of the individual to the group-nation. The sign of Nissan is a lamb, symbol of the group that has only one voice and one purpose, welding the individuals into a unity; the spiritual strength derived from group adherence, as were Israel when they left Egypt. Iyar has the sign of a SHOR, ox, with the particular strengths of each individual as during the weeks of wandering in the desert. The sign of the month of Sivan, of Matan Torah is twins, through the Torah, the avoda of the group and of the individual are merged, supporting and enhancing each other " (Shem MiShmuel).
"Kiddush is the language of invitation" (Onkelos), so G-d said that the people should sanctify themselves for two days and wash their clothes in preparation for Matan Torah. Physical cleanliness is a prior condition for religiosity and spirituality; "A convert who was circumcised but who has not immersed himself is not yet converted" (Yevamot 46b). This is repeatedly demonstrated in the avoda of the kohanim and in our own everyday ritual, eating and praying. However, in many religions and sects, sexual immorality is often associated with spiritual ecstasy; even in Israel's worship of the calf, we read: "the nation rose L'TZACHEIK - sexual immorality" (Rashi, Shmot 32:6).
"Moshe added, 'be prepared for three days, come not near your wives" (Sh'mot 19:14). In effect he said: 'separate yourselves from sin, desist from stealing, and distance yourselves from all detestable actions, so that you may be pure to receive Torah'. Later Yehoshua (3:5) said: 'prepare food and do Teshuva so that you may enter Eretz Yisrael" (Eliyahu Rabbah 18). "When we shall desist from fraudulent dealings, the nations of the world will demand of G-d that He redeem such a pious nation, and the long galut will end" (S'mag, Hilkhot HaShavat Aveida).