Abel was a prophet, one who was foretelling the coming of Jesus our Messiah, the Serpent Crusher:
"And I will put enmity between thee and the woman, and between thy seed and her seed; it shall bruise thy head, and thou shalt bruise his heel." (Genesis 3: 15)
It is very likely that when Cain sought to speak with Abel, just before he killed him, that Abel was trying to teach him about righteousness before God, based on the blood of Jesus, not the efforts of man:
"And Cain talked with Abel his brother: and it came to pass, when they were in the field, that Cain rose up against Abel his brother, and slew him." (Genesis 4: 8)
John affirms this in this first epistle:
"11For this is the message that ye heard from the beginning, that we should love one another. 12Not as Cain, who was of that wicked one, and slew his brother. And wherefore slew he him? Because his own works were evil, and his brother's righteous." (1 John 3: 11-12)
Jesus recognized Abel as a prophet, too:
"34Wherefore, behold, I send unto you prophets, and wise men, and scribes: and some of them ye shall kill and crucify; and some of them shall ye scourge in your synagogues, and persecute them from city to city: 35That upon you may come all the righteous blood shed upon the earth, from the blood of righteous Abel unto the blood of Zacharias son of Barachias, whom ye slew between the temple and the altar." (Matthrew 23: 34-35)
Abel was righteous before God because of the blood of the lamb, because he walked by faith, not by works.
Today, we are made righteous not by the blood of bulls and goats, but the blood of Jesus!
"For he hath made him to be sin for us, who knew no sin; that we might be made the righteousness of God in him." (2 Corinthians 5: 21)
"For it is not possible that the blood of bulls and of goats should take away sins." (Hebrews 10: 4)
So, what do we have that is better than what Abel had? The blood of Jesus!
"But this man, after he had offered one sacrifice for sins for ever, sat down on the right hand of God; 13From henceforth expecting till his enemies be made his footstool. 14For by one offering he hath perfected for ever them that are sanctified." (Hebrews 10: 12-14)
The write of Hebrews explains this power revelaion in great depth in the previous chapter:
"11But Christ being come an high priest of good things to come, by a greater and more perfect tabernacle, not made with hands, that is to say, not of this building; 12Neither by the blood of goats and calves, but by his own blood he entered in once into the holy place, having obtained eternal redemption for us. 13For if the blood of bulls and of goats, and the ashes of an heifer sprinkling the unclean, sanctifieth to the purifying of the flesh: 14How much more shall the blood of Christ, who through the eternal Spirit offered himself without spot to God, purge your conscience from dead works to serve the living God?" (Hebrews 9: 11-14)
"Jesus the mediator of the new covenant, and to the blood of sprinkling, that speaketh better things than that of Abel." (Hebrews 12: 24)
"But if we walk in the light, as he is in the light, we have fellowship one with another, and the blood of Jesus Christ his Son cleanseth us from all sin." (1 John 1: 7)
Abel was made righteous by blood. We have been cleansed forever by the blood of Jesus, which speaks better things!