Abel's offering was a blood offering (Hebrews 9:22).
Abel proved his faith by the offering which he brought and
he obtained witness from God that he was "righteous" (Hebrews 11:4).
Abel's offering was an example of the "Lamb of God,
which taketh away the sin of the world" (John 1:29).
Today we receive righteousness by believing "the gospel
... by which we are saved ... that Christ died for our sins according to the Scriptures; and that He was buried,
and that He arose again the third day according to the Scriptures" (I Corinthians 15:1-4).
"But without faith it is impossible to please Him,
for he that cometh to God must believe that He is, and that He is a rewarder of them that diligently seek Him."