Genesis chapter 4 narrates the sacrifices which Cain and Abel brought to God and the events which followed. You should consider reading the chapter and see if these thoughts fit with what the Bible says:
Cain and Abel both brought sacrifices to God. Abel’s was acceptable and Cain’s was not. The book of Hebrews tells us that Abel offered a sacrifice by faith (11:4). If we accept what Paul said in Romans (10:17) that faith come by hearing the Word of God, the we are safe to conclude that God told them what was acceptable and that one did it, while the other did not. In other words, God does not make us guess about what is pleasing to Him, he clearly lays it out for us.
Of course, the problem was not just an incorrect sacrifice, but the reaction to God’s rejection of that sacrifice. Cain got angry! His countenance fell. In other words, he was highly upset that his sacrifice was not accepted and perhaps even more upset that Abel’s had been. Yet God still took time to talk with Cain, encourage him to do right and warn him about the consequences of doing wrong.
Cain, however, choose to reject God’s counsel and do things his own way. He reacted by killing his own brother. Whatever the motive for Cain to do this (and many have been suggested), Cain did not rule over sin. He allowed sin to rule over him. He soon found out that the consequences were more difficult than if he had simply humbled himself before God and had done what he had been asked to do.
The lesson we can learn for ourselves is that, even today, God has not left himself without a testimony of what He wants from those who will follow Him. However, many of those who want (say they want) to follow Him do not even take a moment to read what God has said. They go through life, offering up sacrifices which God neither requested nor desired. They should not be surprised when God rejects the sacrifice and suggests that “if they do well, they will be accepted”.
Are we like Cain who does not listen to God’s word or are we like Abel who did…and through it, though he is dead, he still speaks?