Today many people laugh at the idea of redemption but this became necessary when sin entered the world and separated man from God back in the garden of Eden.  When the first couple Adam and Chava disobeyed Yahweh and ate the fruit (citrus), sin entered and separated them from God.  From that point on the only way or means of bridging this separation of man from God was the means of blood to atone our sins.  This bridging  is not only called redemption but also reconciliation unto Yahweh.  In the history of Yahweh dealing with his covenanted people the means of redemption was always by blood.

The redemptive element of blood begins to come into the theme of Scripture at the same time that sin does, for until sin came, no blood was necessary.  We read that just as soon as man is expelled from the Garden of Eden: "Yahweh (God) made for Adam and for his wife coats of skins, and clothed them" (Genesis 3:21).  This shows that more then one animal had to be killed and the Jewish sages believe that Yahweh Himself killed or did the first sacrifice of rams to cover Adam and Chava.

The skins were animal skins.  The nakedness, that the element of sin now revealed, needed to be covered.  But the covering required the death of several animals and so for the first time in history, blood was shed.  This provides the root meaning of the Hebrew word Kippur for atonement, which is "a covering" or expiation.

The necessity of blood was a lesson soon learned by the sons of the first human couple.  The time came for both Abel and Cain to bring their sacrifices before God.  Cain offered for sacrifice the fruit of his labours in the field that he thought best.  The offering was vegetarian based, and it was without blood.  Abel brought a blood offering taken from his flock.  When Yahweh passed judgment on the two types of offerings, that of Cain was rejected and that of Abel was accepted.  So a lesson was taught to humanity, one cannot approach God by whatever means we choose.  It is man who has sinned and offended the holy God, it is God who must do the forgiving and setting out the criteria.  Therefore, it is not for man to choose the means of forgiveness or offering but for God, and God has chosen the means to be the blood of set animals.  Cain had chosen to approach God in his own way, but was rejected, alas this is what most of the world population tries to do, they make God something of a myth and choose their own way of salvation but fail.

In the Torah there was only one way of people going to heaven and that was through grace of God.

Adam and Chava had to find that out for themselves. After they had sinned we find the following account:-

Genesis 3:7And the eyes of them both were opened, and they knew that they were naked; and they sewed fig leaves together, and made themselves aprons.

Notice three things
1. They did works to "cover" themselves.
2. The covering was made of herbage.
3. The covering was incomplete - it was only "aprons".

This is man made religion.  Like Islam, Humanism, Buddhism. God will not accept this!

That is why we find a little later God showing His displeasure at the covering.

Genesis 3:21 Unto Adam also and to his wife did the LORD God make coats of skins, and clothed them.

Notice three things
1. the LORD God did the works.
2. the covering was made of skins (an animal had to die)
3. the covering was complete - coats instead of aprons.

It's your choice, you can come to God with your own righteousness and covering (rags and aprons) which is inadequate or you can accept His provision– Jesus Christ on the cross, be completely covered once for all.

Abel chose the way God demanded, and was accepted.  As Biblical history develops in the book of Genesis, we find that all those with whom God was pleased came to Him by means of blood of the required animals not just any blood.  Noah immediately offered up blood sacrifices of clean animals when he left the Ark.  He was followed by other similar great men in the history of the Hebrews - Abraham, Isaac, Jacob - All of whom were careful to approach God by means of blood.

When Moses received the Law at Mount Sinai, the redemptive element of blood of clean animals ran through the entire Torah with it's 613 commandments.  Yahweh rounded up the whole thing by the following verse.

Leviticus 17:11 For the life of the flesh is in the blood, and I have given it to you upon the altar to make atonement for your souls; for it is the blood that maketh atonement by reason of the life. 

It can easily be said that all of the Law revolves around this one statement above.  There are commandments which God gave in the law that were to be obeyed.  Disobedience was sin.  If disobedience did take place, the means of atonement for the sin was blood.  The book of Leviticus opens by giving great details to different types of blood sacrifices of the set apart animals not just any animal of your choosing.  All these different sacrifices had the same purpose; that Israel might be rightly related to God.  All seven feasts of Israel - Passover, Unleavened Bread, First fruits, Pentecost, Trumpets, Day of Atonement and Tabernacles - required the shedding of blood.  The Yom Kippur ceremony was greatly detailed in Leviticus 16, where careful instructions were given for the shedding of blood to atone for the sins of the Hebrew nation.  

The tabernacle and the Temple were both built to facilitate and to reveal Yahweh's grace upon His people the requirement of shedding of blood for the atonement for the people's sin.  The Holy of Holies, which contained the Shechinah Glory, the visible manifestation of the presence of God, could only be entered once a year, by only one man, the High Priest.  In order for him to enter, he had to have the blood of the Yom Kippur sacrifice with him, and this blood has to be sprinkled on the Ark of the covenant, which contained the Tablets of the Law itself:  Notice the blood was not just any blood but of the specified animals in Leviticus chapter 11, he would dare not sacrifice a swine and use its blood as had been used by foreign cultures.

Leviticus 16:15-17 Then shall he kill the goat of the sin-offering, that is for the people, and bring his blood within the veil, and do with his blood as he did with the blood of the Bullock, and sprinkle it upon the mercy-seat, and before the mercy-seat; and he shall make atonement for the holy place, because of the uncleannesses of the children of Israel, and because of their transgressions, even all their sins; and so shall he do for the tent of meeting, that dwelleth with them in the midst of their uncleannesses.  And there shall be no man in the tent of meeting when he goeth in to make atonement in the holy place, until he come out, and have made atonement for himself, and for his household, and for all the assembly of Israel.

Why did Y'shua have to die?