In line with that, one reference work defines “sacrifice” as “a religious rite in which an object is offered to a divinity in order to establish, maintain, or restore a right relationship of man to the sacred order.”

9. (a) In what did Abel put faith, and how did he express it? (b) What did Abel’s offering accomplish?

⁹ Abel’s faith was not just faith in God in general, which Cain must also have had. Abel had faith in God’s promise of a Seed to bring about the salvation of faithful humans. It was not revealed to him how that would be worked out, but God’s promise made Abel aware that someone would have to be bruised in the heel. Yes, he apparently concluded that blood would have to be shed​—the very idea of sacrifice. Abel offered a gift involving life and blood to the Source of life, likely as a token of his intense longing for and in anticipation of the realization of Jehovah’s promise. This expression of faith was what made Abel’s sacrifice pleasing to Jehovah, and in a limited way, it expressed the essence of sacrifice​—a means by which sinful humans can approach God to gain his favor.​—Genesis 4:4; Hebrews 11:1, 6.

10. How was the significance of sacrifice made clear by Jehovah’s asking Abraham to offer up Isaac?

¹⁰ The profound significance of sacrifice was made dramatically clear when Jehovah commanded Abraham to offer up his son Isaac as a burnt offering. Although that sacrifice was not literally carried out, it served as a picture of what Jehovah himself would eventually do​—offer up his only-begotten Son as the greatest sacrifice ever in order to accomplish His will toward mankind. (John 3:16)