Hebrews 11:4-6

By faith Abel offered God a better sacrifice than Cain did. By faith he was commended as a righteous man, when God spoke well of his offerings. And by faith he still speaks, even though he is dead. By faith Enoch was taken from this life, so that he did not experience death; he could not be found, because God had taken him away. For before he was taken, he was commended as one who pleased God. And without faith it is impossible to please God, because anyone who comes to him must believe that he exists and that he rewards those who earnestly seek him.

By faith he was commended as a righteous man
Hebrews 11:2 This is what the ancients were commended for.
Hebrews 11:39 These were all commended for their faith, yet none of them received what had been promised.

when God spoke well of his offerings
Genesis 4:4 But Abel brought fat portions from some of the firstborn of his flock. The LORD looked with favor on Abel and his offering, ...
1 John 3:12 Do not be like Cain, who belonged to the evil one and murdered his brother. And why did he murder him? Because his own actions were evil and his brother's were righteous.

And by faith he still speaks, even though he is dead
Hebrews 12:24 ... to Jesus the mediator of a new covenant, and to the sprinkled blood that speaks a better word than the blood of Abel.

he could not be found because God had taken him away
Genesis 5:21-24 When Enoch had lived 65 years, he became the father of Methuselah. And after he became the father of Methuselah, Enoch walked with God 300 years and had other sons and daughters. Altogether Enoch lived 365 years. Enoch walked with God; then he was no more, because God took him away.

because anyone who comes to him must believe that he exists
Hebrews 7:18-19 The former regulation is set aside because it was weak and useless (for the law made nothing perfect), and a better hope is introduced, by which we draw near to God.
Jeremiah 29:13 "You will seek me and find me when you seek me with all your heart."

NOTES:
Cain and Abel - Genesis 4:2-12
Enoch - Genesis 5:18-24
Psalm 49:15
Read Ephesians 2

Scriptures taken from the Holy Bible, New International Version® NIV®, Copyright© 1973, 1978, 1984 by International Bible Society. Used by permission. All rights reserved worldwide.