Question: Why did Adam and Eve cover themselves with fig leaves? Was the minute Adam and Eve ate of the fruit of the Tree of Life the first time sin came into the World?
Answer: The Bible doesn’t tell us why Adam and Eve only made "aprons" (Genesis 3:7); but they didn’t do the job of covering nakedness! God had to shed the blood of animals to make coats of skin for them. The "aprons" represented man’s efforts to cover their sin, or self-righteousness. The fig leaves didn’t do the job there, either.
When God made the coats of skin, He laid down a principle,
"...without the shedding of blood there is no remission (of sin)." - Hebrews 9:22b
The innocent victims, the animals, had to die to make the covering for sin. The animals were sacrificed, they had no part in the disobedience. Adam and Eve accepted the sacrifice and wore the coverings. This was the beginning of sacrifices to "cover" sin until the perfect Lamb of God, our Savior, the Lord Jesus Christ came to die as the perfect substitute "which taketh away the sins of the world." (John 1:29).
When Adam and Eve ate of the forbidden fruit, sin came into the perfect world God had created for them, by the entrance of a sin nature, passed on through Adam and Eve to the whole human race. We find that "...death passed upon all men." (Romans 5:12b).
Adam and Eve began to die physically; and they died spiritually, until they accepted God’s sacrifice for them. Spiritual death passed on to all humanity. Now, as the Bible says, "...all have sinned." (Romans 5:12c). The sin spoken of here is our sin nature inherited from Adam and Eve. All mankind is born with a sin nature; and, until they receive Jesus Christ as their Savior, they are separated from God and "...dead in trespasses and sins." (Ephesians 2:1) We are not sinners because we sin; but, we sin because we are born sinners.
The Bible says that sin was already in the universe. Who met Eve in the Garden of Eden? (Genesis 3:1) It was Satan, of course! Already operating in his malicious character. He had already fallen from his exalted position of anointed cherub, and as "Lucifer, son of the morning." (Isaiah 14:12 and Ezekiel 28:14,15). He had already influenced a third of the angels to follow him. (Revelation 12:3,4). The Bible states the angels were created before God laid "the foundation of the earth." (Job 38:4-7). The "sons of God" referred to here are the angels.
Satan thought he would ruin God’s perfect plan; but, he is no match for God! God knew we would need a Savior and foreordained Him "before the foundation of the world..." (1 Peter 1:18-20). I hope you have trusted Him as your Savior.