Adam Clarke on Genesis 4:5

Unto Cain - As being unconscious of his sinfulness, and consequently unhumbled, and to his offering, as not being accompanied, as Abel's was, with faith and a sacrifice for sin, he had not respect - He could not, consistently with his holiness and justice, approve of the one or receive the other. Of the manner in which God testified his approbation we are not informed; it was probably, as in the case of Elijah, by sending down fire from heaven, and consuming the sacrifice.

Cain was very wroth - That displeasure which should have been turned against his own unhumbled heart was turned against his innocent brother, who, though not more highly privileged than he, made a much better use of the advantages which he shared in common with his ungodly and unnatural brother.