According to Calvinists, why did God say what He did to Cain in Genesis 4:7?

Both high and low Calvinists from this Wiki say that God authorized the Fall, by which all deserve to be condemned. Me: If there is no predestination at all, both Cain and Abel will end up in hell. From this link Calvinists teach that Ephesians 2:8 declares that *faith is given to the elect only.* Now, Hebrews 11:4 says: > By *faith* Abel brought God a better offering than Cain did. ([NIV](https://www.biblegateway.com/passage/?search=Hebrews+11%3A4&version=NIV) , italics added) Me: because there is predestination, Abel will end up in heaven while Cain will still end up in hell. But [Genesis 4:7](https://www.biblegateway.com/passage/?search=genesis+4%3A7&version=NIV) says: > If you do what is right, will you not be accepted? But if you do not > do what is right, sin is crouching at your door; it desires to have > you, but you must rule over it. (NIV) My question: If God alone before the creation had already decreed that Cain would end up in hell, and that's why He will never give Cain faith, why did God say what He did to Cain in Genesis 4:7?