When you work the ground, it will no longer yield its crops for you. You will be a restless wanderer on the earth. (Genesis 4:12, NIV)
Genesis 4 introduces Cain and Abel. Abel kept flocks, and Cain did farming. In the course of time, they brought what they gained as an offering to the Lord. However, their heart to God was different. Cain brought some of the fruits of the soil as offerings, and Abel brought the firstborn of his flock and some of their fat portions. It means Cain offered a perfunctory sacrifice to the Lord with what was unimportant to him, and Abel offered the most precious things. Therefore, God received Abel’s offering but did not accept Cain’s. They were different in their fear of God. Abel sincerely feared and loved God through deep fellowship with Him and also knew what the real value was, so he was able to offer sacrifices by faith.
In this, we learn that knowing God is alive is different from loving Him. Cain knew that God was alive, and he could communicate with Him. However, he did not love God with all his heart, so God did not receive his offering.
Cain got angry because of it. He felt uncomfortable, and his face was downcast with his anger. The hatred toward Abel began to erode Cain, and God told him he must control sin. However, Cain did not listen to the word of God and grew more hostile to Abel. He began to plan how to kill Abel and finally decided to carry it out.