Rabbi Elie Munk - Call Of The Torah:
21.  Garments of skin.  Our Sages differ on what "garments of skin" means.  For some, they are garments made of the skin of animals.  For others, they are garments for the skin, covering the skin but not the soul of man.  Rabbi Yehudah teaches that before the sin, man was enveloped in a halo of light.  He appeared in a majestic splendor before all the creatures of heaven and earth.  The Psalmist is referring to this sublime appearance when he exclaims, "Yet You have made him but slightly less than the angels, and crowned him with soul and splendor" (8:6).  But, after the sin, the halo of glory which illuminated man's spirit disappeared; man was left only with "the garment which covers his skin."  And this is also how to understand the Midrash (Bereishit Rabbah, 20) which states: "The sefer - Torah of Rabbi Meir has garments of light, instead of garments of skin, the two words or and 'or being homonyms.  According to Rambam this version refers to the time before the sin, when man was bathed in light.
The Midrash about Rabbi Meir's sefer-Torah contains an additional idea, according to Rav Yehudah Leib of Gora, Kalwaria, Poland.  Not only the human body but, as it were, all creation was clothed in "garments of skin" after the first sin.  For man is just the reflection of the macrocosm.  Before the sin, all of nature was inundated with the Divine light, which was of resplendent clarity to all creatures.  But after the sin, G-d withdrew to higher spheres and nature became heavily veiled with "garments of skin."  Man could only recognize G-d through this garment which hid G-d from his eyes.  The word 'or "skin" has the same letters as the word 'iver "blind."  These "garments of skin" which envelop the whole universe make man blind.  And yet they are also katnot or "garments of light," since, despite everything, they let the omnipotence of the Creator show through.
The human body, too, is not a hermetically sealed outer cover, for it allows the soul sheltered within to be glimpsed.  But beware the one whose vides and moral degradation cause the skin of his body to be covered with "a tumor, a scab, or a bright spot" and thus obstruct the route leading to the soul.  This man is declared unclean.  "If a person will have on the skin of his flesh, a s'eis or a sapachas or a baheres...and declare him contaminated" (VaYikra 13:2).  
Targum Onkelos
21 And Hashem G-d made for Adam and his wife garments of glory on the skin of their flesh, and He clothed them.
21) Onkelos translates the Biblical phrase katnot 'or as "garments of glory [worn] on the skin of their flesh."
The phrase "garments of the skin," constitutes the basic translation, which is similar to th first explanation presented by Rashi - rather than his second explanation, "garments [made] of skin" (Nefesh HaGer).  The addition of "of glory," may reflect the Midrashic interpretation of R' Meir (in Bereyshit Rabbah 20:12 that treats katnot 'or as katnot or, "garments of light" (Netinah LaGer).
21 From skin.  Rashi points out that the words katnot 'or can be interpreted in two ways:  either as garments on the skin or garments made from skin.  If the former, it refers to garments which cling to the skin as a nail to the finger.  If the latter, to garments made from animal skins or hides (REM). [Ariel Chumash]
Bereishit Rabbah - 20:12
In R. Meir's Torah it was found written, ‘Garments of light (or)' (2) : this refers to Adam's garments, which were like a torch [shedding radiance], broad at the bottom and narrow at the top.
Isaac the Elder said: They were as smooth as a finger-nail and as beautiful as a jewel.
R.Johanan said: They were like the fine linen garments which come from Betshean, (3)
GARMENTS OF SKIN meaning those that are nearest to the skin.
R. Eleazar said: They were of goats’ skin.
R. Joshua said: Of hares’ skin.
R. Jose b. R. Hanina said: It was a garment made of skin with its wool.
Resh Lakish said: It was of Circassian wool, and these were used [later] by first-born children. (4)
R. Samuel b. Nahman said: [They were made from] the wool of camels and the wool of hares,
GARMENTS OF SKIN meaning those which are produced from the skin. (5)
R. Levi said: The Torah teaches you here a rule of worldly wisdom: spend according to your means on food; less than you can afford on clothing, but more than you can afford on a dwelling. Spend according to your means on food, as it is written, "Of every tree of the garden thou mayest freely eat" (Bereyshit 2:16).
Less than you can afford on clothing: AND THE LORD GOD MADE... GARMENTS OF SKIN, AND CLOTHED THEM.(6) More than you can afford on a dwelling: for lo! they were but two, yet they dwelt in the whole world. (7)

(2)  Or (light), instead of 'Or (skin).
(3) V. supra, 19:1.
(4) When they used to perform the sacrificial service, before the priests were chosen for it; v. infra, 63:13; Bamidbar R. 4:8.
(5) Viz. the wool that comes off it.
(6) I.e. only simple, not expensive garments.
(7) Cf. Pes. 114a; Hul. 84b.

Zohar, Shemot, Section 2, p. 229b
As soon as he was driven from the Garden of Eden and had need of forms suited to this world, “the Lord God”, Scripture says, “made for Adam and for his wife garments of skin ('or), and clothed them” (Bereishit 3:21). Formerly they were garments of light (or), to wit, of the celestial light in which Adam ministered in the Garden of Eden. For, inasmuch as it is the resplendency of the celestial light that ministers in the Garden of Eden, when first man entered into the Garden, the Holy One, blessed be He, clothed him first in the raiment of that light. Otherwise he could not have entered there. When driven out, however, he had need of other garments; hence “garments of skin”. So here also “they made residual garments to minister in the holy place”, so as to enable the wearer to enter the Sanctuary. Now, it has been already taught that a man's good deeds done in this world draw from the celestial resplendency of light a garment with which he may be invested when in the next world he comes to appear before the Holy One, blessed be He. Appareled in that raiment, he is in a state of bliss and feasts his eyes on the radiant effulgence. So Scripture says: “To behold the graciousness of the Lord, and to visit early in his temple” (Tehillim 27:4). Man's soul is thus attired in the raiments of both worlds, the lower and the upper, thereby achieving perfection. Of this Scripture says: “Surely the righteous shall give thanks unto thy name”; to wit, in this world-”The upright shall dwell in thy presence” (Ibid. 140:14); namely, in the other world.’
 Zohar, Shemot, Section 2, Page 210a-b
The righteous are illumined by the reflection of that supernal resplendency, and on each New Moon the glory of the Shekinah as revealed in that firmament transcends that of other times. All the righteous then approach and prostrate themselves before it. Happy is the portion of whoever is found worthy of those garments wherein the righteous are clad in the Garden of Eden. Those garments are made out of the good deeds performed by a man in this world in obedience to the commands of the Torah. In the Lower Paradise man's soul is thus sustained by these deeds and is clad in garments of glory made out of them. But when the soul mounts up on high through that portal of the firmament, other precious garments are provided for it of a more exalted order, made out of the zeal and devotion which characterized his study of the Torah and his prayer; for when that zeal mounts up on high a crown is made out of it for him to be crowned with, but some of it remains as the man's portion, out of which garments of light are made for the soul to be clad in when it has ascended on high. The former garments, as we have said, depend on his actions, but these depend on his devotion of spirit, so as to qualify their owner to join the company of holy angels and spirits. This is the correct exposition of the matter as the Holy Lamp learned it from Elijah. The garments of the Lower Paradise are made of man's actions; those of the celestia; Paradise of the devotion and earnestness of his spirit.