In the Old Testament, God never demanded human sacrifice but was disgusted by it.
Let no one be found among you who sacrifices their son or daughter in
the fire, who practices divination or sorcery, interprets omens,
engages in witchcraft. (Deuteronomy 18:10, NIV)
He followed the ways of the kings of Israel and even sacrificed his
son in the fire, engaging in the detestable practices of the nations
the LORD had driven out before the Israelites. (2 Kings 16:3, NIV)
God did not want Abraham to actually sacrifice his son Isaac(Ismael according to Muslims), God was only testing his faith.
Some time later, God tested Abraham’s faith. “Abraham!” God called.
“Yes,” he replied. “Here I am.” “Take your son, your only son—yes,
Isaac, whom you love so much—and go to the land of Moriah. Go and
sacrifice him as a burnt offering on one of the mountains, which I
will show you.” (Genesis 22:1-2, NLT)
God actually felt good when He smelled the aroma of burning animals.
Then Noah built an altar to the LORD and, taking some of all the clean
animals and clean birds, he sacrificed burnt offerings on it. The
LORD smelled the pleasing aroma and said in his heart: "Never again
will I curse the ground because of humans, even though every
inclination of the human heart is evil from childhood. And never again
will I destroy all living creatures, as I have done. (Genesis 8:20-21,
You are to wash the internal organs and the legs with water, and the
priest is to burn all of it on the altar. It is a burnt offering, a
food offering, an aroma pleasing to the LORD. (Leviticus 1:9, NIV)
and the priest will burn them on the altar. It is a special gift of
food, a pleasing aroma to the LORD. All the fat belongs to the
LORD. (Leviticus 3:16, NLT)
Then burn the entire ram on the altar. It is a burnt offering to the
LORD, a pleasing aroma, a food offering presented to the LORD.
(Exodus 29:18, NIV)
However, God only forgave their sins temporarily because animal sacrifice cannot remove sins, it only covers it temporarily. It is important to know that animal blood was only for forgiveness of sins, not for the removal of sins.
In fact, the law requires that nearly everything be cleansed with
blood, and without the shedding of blood there is no forgiveness.
(Hebrews 9:22, NIV)
It is impossible for the blood of bulls and goats to take away sins.
(Hebrews 10:4, NIV)
Only the blood of Jesus can take away our sins.
The next day John saw Jesus coming toward him and said, “Look, the
Lamb of God, who takes away the sin of the world! (John 1:29, NIV)