Genesis 4:10

The voice of thy brother's blood - It is probable that Cain, having killed his brother, dug a hole and buried him in the earth, hoping thereby to prevent the murder from being known; and that this is what is designed in the words, Thy brother's blood crieth unto me From The Ground - which hath opened her mouth to receive it from thy hand. Some think that by the voice of thy brother's blood the cries of Abel's widow and children are to be understood, as it is very probable that he was father of a family; indeed his occupation and sacrifices seem to render this probable, and probability is all we can expect on such a subject. God represents these as calling aloud for the punishment of the murderer; and it is evident that Cain expected to fall by the hands of some person who, from his consanguinity, had the right of the avenger of blood; for now that the murder is found out, he expects to suffer death for it. See Genesis 4:14.

What hast thou done? - The Lord now charges him with his guilt: "The voice of thy brother's blood crieth unto me from the soil." In the providence of God blood has a voice crying to him to which he cannot but give heed. It is vain, then, to attempt concealment.

4:10 And he said, What hast thou done? — Thou thinkest to conceal it, but the evidence against thee is clear and uncontestable, the voice of thy brother's blood crieth - He speaks as if the blood itself were both witness and prosecutor, because God's own knowledge testified against him, and God's own justice demanded satisfaction. The blood is said to cry from the ground, the earth, which is said, Genesis 4:11, to open her mouth to receive his brother's blood from his hand. The earth did as it were blush to see her own face stained with such blood; and therefore opened her mouth to hide that which she could not hinder.