In Genesis 3, directly after Adam and Eve eat of the fruit of the knowledge of good and evil, we read that "the eyes of both were opened, and they knew that they were naked. And they sewed fig leaves together and made themselves loincloths" (v.7). No longer did Adam and Eve stand before one another naked and unashamed as they had earlier (Genesis 2:25). Now, they are ashamed and, they cover themselves with a few fig leaves and hide from the LORD God. But both of their attempts (i.e. covering themselves and hiding) ultimately fail. First, their attempt to hide failed, because He is the all-present, all-knowing LORD. He knew exactly where they were and He confronted them (and the serpent) with the consequences of their sin. Second, their covering was not adequate. Instead of fig leaves, the LORD God gives them a new covering of His own making: "And the LORD God made for Adam and and for his wife garments of skin and clothed them" (Genesis 3:21). It is in regard to this second point, that I want to make a few observations.
First, just as Adam and Eve's fig leaves were not a proper covering, sinful men and women cannot cover their nakedness and shame (i.e. sins) by means of good works (Romans 4:4).
Second, just as God provided a proper covering for Adam and Eve, it is God alone who can provide the proper covering for man. In the garden, an animal had to be slain--blood had to be spilt-- in order for Adam and Eve to have garments of skin. And God has done the same for us. He has spilt blood and covered us. But this time, it was not the blood of an animal that was spilt, but it was His own blood--his own life--that was given for us (John 3:16). And it was not with a garment of animal skin that He used to cover us, but it was with Himself--with His own rightousness--that He clothed us with.
Of course, what we have been discussing is the doctrine of imputation (foreshadowed in the book of Genesis) in which Christ was counted as having our sin (though He Himself was sinless) and we are counted as having God's righteousness (though we ourselves are not righteous.) "For our sake he made him to be sin who knew no sin, so that in him we might become the righteousness of God" (2 Corinthians 5:21). Let us praise God for taking our sin upon Himself and counting us righteous in Christ. What a gracious and awesome God!