“Do right!” John harped on that time and time again. Love others? Of course, and while he had connected doing right to loving others he had not placed as full an emphasis upon it. Verse 10 coupled these two themes, and as we traipse into verse 11, we see John jump into love for others with both feet.
11 For this is the message that you have heard from the beginning, that we should love one another. 12 We should not be like Cain, who was of the evil one and murdered his brother. And why did he murder him? Because his own deeds were evil and his brother’s righteous. (1 John 3:11-12–ESV)
“Love one another.” John had emphasized the importance of behavior. The best example of that was loving others, and that message of Christianity was taught by the apostles as they entered community after community. Being entry level Christianity it was on the curriculum from the beginning. By loving others, they walked as Jesus walked. That was righteous living. John mentioned this in chapter 2 verse 7 1 and link here if you want to delve further into the lesson on that passage.
What happened before Cain came?
John takes up the case of Cain to teach of love and hate, but for a moment let us consider events in the first family. God launched this family. One rule they were given: eat of this tree, and you will begin the path to death. “Dying you shall die,” is how the author of Genesis phrased it. Well, what happened? Satan got his deceptions inserted into the mix, they fell, and all things began their terrible wind-down.
God did not dust his hands of humanity. Knowing they would choose the tree he was ready for it, even though expelled from the garden they were not left alone. In fact, he gave a new rule: animal sacrifice will lead you home. They would still die, but the blood of the sacrifices would pave the way for the undoing of their sin.
As Adam and Eve went on about their not-so-merry way, they eventually had their first couple of kids. Cain was the firstborn and Abel second. They grew up predictably both becoming farmers: Cain of crops and Abel animals. Religious practice was part of their lives from the earliest times Cain and Abel’s legacy stemming directly from the religious routine of sacrifice.
God taught Adam and Eve the importance of animal sacrifice after expelling them from the paradise of Eden. Humanity, now fallen, must never forget that the deed in the Garden broke the connection to God. God, desiring restoration, set before this family the way back.