We learn an important lesson from Cain and God’s interaction over a moment when the
offering is presented. Abel’s offering is in faith: obedience to the instruction that he had
received. Cain’s offering is not in faith: he disobeyed God in something. Whatever it was
it was enough to open the door for greater sin to come in… anger and murder. The
essential aspect of disobedience was to a) despise instruction from God and b) believe
that his own way of presenting the offering was right before God. I don’t know if he
missed the time, type or anything else regarding the offering but I know that He did not
tremble at God’s word and therefore there was no obedience to what the Lord had told
him to do. In Acts 5 Ananias and Shaphira also thought they knew better. The Holy
Spirit had been leading disciples to bring big offerings to the apostles. Ananias and
Shaphira wanted to keep part of the proceeds from the sale of their property. However,
Peter confronts them saying that they had not lied to men but to the Holy Spirit. They
both died because they walked the way of Cain.

Original Hebrew gives a bit more clarity on this lesson of faith that Abel teaches us.
‘Now Abel WAS a shepherd, and Cain WAS a farmer.’ In Hebrew the word used is ‘VaYehi’ when speaking about Abel but ‘Hayah’ in the case of Cain.

The first word suggests that ‘it was forced upon’ Abel while the second word ‘Hayah’ indicates that it was a
‘choice’ for Cain. Cain may have been instructed to do Abel’s type of work. If you
consider the scripture carefully you can see that Cain’s offering was “some” of the
product of the soil but Abel’s was “fat portions from the firstborn of his flock.” It is not
clear that Cain brought from his crops and that it was the best part. However, Abel
brought his best and used his offering as a representation of his life before God.
Some of these insights are gathered from https://www.hebrewversity.com/ For those
interested in basic Biblical Hebrew.