John Calvin Commentary Genesis 4:14

"Behold, thou hast driven me out this day from the face of the ground; and from thy face shall I be hid; and I shall be a fugitive and a wanderer in the earth; and it will come to pass, that whosoever findeth me will slay me." — Genesis 4:14 (ASV)

Every one that findeth me. Since he is no longer covered by the protection of God, he concludes that he will be exposed to injury and violence from all people. And he reasons justly; for the hand of God alone marvelously preserves us amid so many dangers. And those who have said that our life not only hangs on a thread but also that we have been received into this fleeting life from the womb, from a hundred deaths, have spoken prudently.

Cain, however, in this situation, not only considers himself as deprived of God’s protection but also supposes all creatures to be divinely armed to take vengeance for his impious murder. This is the reason he so greatly fears for his life from anyone who might meet him. For since humans are social animals and all naturally desire mutual interaction, it is certainly to be regarded as a portentous fact that meeting any person was formidable to the murderer.