Sacrifices were Accepted when offered in Sincerity and Faith
Source: TTT
Genesis 4:4
while Abel brought the best portions of the firstborn of his flock. And the LORD looked with favor on Abel and his offering,
Hebrews 11:4
By faith Abel offered God a better sacrifice than Cain did. By faith he was commended as righteous when God gave approval to his gifts. And by faith he still speaks, even though he is dead.
Genesis 8:21
When the LORD smelled the pleasing aroma, He said in His heart, “Never again will I curse the ground because of man, even though every inclination of his heart is evil from his youth. And never again will I destroy all living creatures as I have done.