Able's sacrifice was pleasing to God not because it was the right kind of sacrifice, it probably was, but because Able respected God, his heart was right with God.
Cain was not rejected by God for the wrong kind of sacrifice, it probably was, but God rejected him because his heart was evil, he did not respect God and disrespected Able for being loved by God.
We have proof that Cain did not respect God, that proof was that he killed the one that God loved, the one that loved God. The rage Cain felt led him to end the relationship between God and Able or so it was in his own mind. Killing Able did not destroy the relationship between God and Able, but it did destroy the relationships between God and Cain.
Those who demonstrate jealousy toward others have murder in their heart. Not because Cain killed Able, but because jealousy is hatred an absence of love, God says if we hate then we have murder in our hearts.
1 John 3:15
"Everyone who hates his brother is a murderer, and you know that no murderer has eternal life abiding in him."
To be angry toward someone merely because they have something we want and can't have, is hatred. When we choose not to engage in their joy with them over their accomplishment or pleasure, we are demonstrating hatred and revealing the murder that dwells in our heart.
Romans 12:15-16 " 15 Rejoice with those who rejoice; weep with those who weep. 16 Live in harmony with one another. Do not be proud, but enjoy the company of the lowly. Do not be conceited."
It is common for the jealous person to refrain from engaging in the emotions of others because they cannot stand that the one they are jealous of is enjoying something. If the joy is not about them, then they have a desire to ruin the happiness of those that have the joy.
Those who feel a need to be superior to others will often demonstrate jealousy. Cain wanted to be superior to Able, when he saw that he was not and that his sacrifice was not acceptable, he allowed the rage in his heart to escalate into murder.
Cain could not ruin Able because God was on Able's side, so his hatred for God and for Able caused him to commit murder out of rage, at the two who caused his pain. Raging to cause hurt or becoming stone faced is a way of killing the other person off. even if the jealous person does not actually commit murder.
Ignoring others because of jealousy or ruining whatever they accomplished are tactics that are often used by jealous people. Jealousy can only exist when there is a deep and intense self focus.
If we are to refrain from jealousy we must have our own joy based in our relationship with Christ. When Christ is our focus we do not feel a need to be superior, nor do we want what others have so much so that we are willing to destroy relationships and reputations.
Think about it! What does anyone accomplish by their jealousy? The only thing they accomplish is continual trauma in their own soul and destroyed relationships. If we find ourselves involved in jealous feelings or thoughts, then it is time to confess that sin before it ruins someone.
