Genesis 4:8

Cain talked with Abel. The subject of Cain’s talk with his brother is not stated. The RSV, following the Samaritan Version and the LXX, has added the words, “Let us go out into the field.” This clause appears to be a copyist’s addition, though the context makes it entirely possible that the original read thus. It is improbable that Cain told Abel what God had just said to him, but he may have tried to argue with his brother, accusing God of unrighteousness in His dealings with him.

When they were in the field. Cain’s “works were evil and his brother’s righteous” (1 John 3:12). That is why Cain killed his brother. Enmity between good and evil, predicted by God before the expulsion from the garden, was seen now for the first time in its most horrible form. Twice in this verse the words “his brother” are added to the name of Abel to bring out clearly the horror of Cain’s sin. In him the seed of the woman had already become the seed of the serpent. Cain’s crime revealed the true nature of Satan as “a murderer from the beginning” (John 8:44). Already there had sprang up that contrast of two distinct “seeds” within the human race, a contrast that runs through the entire history of mankind.