Moses
Genesis 4:8ESV·traditional attribution

Cain spoke to Abel his brother. And when they were in the field, Cain rose up against his brother Abel and killed him.

John Calvin Reformed @genevareformer

8. And Cain talked with Abel his brother . Some understand this conversation to have been general; as if Cain, perfidiously dissembling his anger, spoke in a fraternal manner. Jerome relates the language used, ‘Come, let us go without.’ “Egrediamur foras.” — Vulgate. In my opinion the speech is elliptical, and something is to be understood, yet what it is remains uncertain.

Matthew Henry Presbyterian @wholebiblehenry

We have here the progress of Cain's anger, and the issue of it in Abel's murder, which may be considered two ways: - I. As Cain's sin; and a scarlet, crimson, sin it was, a sin of the first magnitude, a sin against the light and law of nature, and which the consciences even of bad men have startled at. See in it, 1.

John Gill Reformed Baptist @doctorgill

And the Lord said unto Cain, where is Abel thy brother?.... Perhaps this was said to him the next time he came to offer, he not being with him: this question is put, not as being ignorant where he was, but in order to bring Cain to a conviction and confession of his sin, to touch his conscience with it, and fill it with remorse...