4 By faith Abel offered to God a more excellent sacrifice than Cain, through which he obtained witness that he was righteous, God testifying of his gifts; and through it he being dead still speaks.
a more excellent sacrifice — by shedding blood, Abel acknowledged that he was a sinner and that the righteous punishment for sin was death
through which — by the sacrifice, it was seen that Abel was righteous
gifts — plural — Abel regularly brought sacrifices
God bore witness to the efficacy of Abel’s sacrifice because he came to God in the appointed way. He had faith in God’s revelation concerning sin and the need for a substitution.
speaks — by example or that salvation is through blood (Hebrews 12:24). Jesus’ blood is better than Abel’s (Romans 5:9)
And in the process of time it came to pass that Cain brought an offering of the fruit of the ground to the LORD. Abel also brought of the firstborn of his flock and of their fat. And the LORD respected Abel and his offering, but He did not respect Cain and his offering. And Cain was very angry, and his countenance fell (Genesis 4:3-5).