In Genesis 3:7 Adam and Eve tried to cover their sin with fig leaves. Nakedness was a word used in Hebrew thought to denote being found out - uncovered - sinful. When God saw them He could not accept their covering so animals were sacrificed and 'The Lord God made coats of skin and clothed them' Genesis 3:21. The Bible is not specific however most agree the animals would have been lambs or young sheep. Now rush forward a few thousand years and hear the words of John the Baptist on spotting Jesus "Behold the Lamb of God who takes away the sin of the world" John 1:29. However Jesus sacrifice on the cross didn't just Cover sin it took it away from all those who are trusting in Him for their salvation. Working for salvation by being good or doing good deeds are fig leaves and unacceptable to God. The only sacrifice God will accept to cover and takeaway our sin is the sacrifice of His Son in the work of the cross. This is why Good Friday is Good news to all those who believe!