Thank you for contacting BibleAsk.
After Cain killed his brother Abel, God said: “And now you are cursed from the ground, which has opened its mouth to receive your brother’s blood from your hand. When you work the ground, it shall no longer yield to you its strength. You shall be a fugitive and a wanderer on the earth” (Genesis 4:11-12).
Sometimes life is more punishment than death. And because Cain believed life would be worse for him than death. He said to God, “My punishment is greater than I can bear. Behold, you have driven me today away from the ground, and from your face I shall be hidden. I shall be a fugitive and a wanderer on the earth, and whoever finds me will kill me” (Genesis 3:13-14).
Previously, Cain had been “a tiller of the ground” (Genesis 4:2, NKJV), so this particular punishment took away his livelihood. Cain had misused the fruits of the ground. God would no longer permit him to gain his livelihood by tilling the soil. A wanderer in the earth (vs. 14, 16), whether shepherd or nomad, cannot be a successful farmer. Cain was doomed to a life of perpetual wandering in order to secure food for himself, his family, and his beasts.
In addition, Cain feared death at the hands of another person. To prevent others from killing Cain, God marked him somehow (what type of mark is uncertain). Instead of being put to death, Cain was forced to live the rest of his life with unfruitful work and the guilt of having killed his brother.
In His service,