Then again she became with child and gave birth to Abel, his brother. And Abel was a keeper of sheep, but Cain was a farmer. And after a time, Cain gave to the Lord an offering of the fruits of the earth. And Abel gave an offering of the young lambs of his flock and of their fat. And the Lord was pleased with Abel’s offering; But in Cain and his offering he had no pleasure. And Cain was angry and his face became sad. And the Lord said to Cain, Why are you angry? and why is your face sad? If you do well, will you not have honour? and if you do wrong, sin is waiting at the door, desiring to have you, but do not let it be your master. (Genesis 4:2-7, Bible In Basic English)
The art of true giving comes from the heart and not out of obligation. We are under the dispensation of grace and not the law as Israel was. Therefore, the majority of that nation have shown us what not to do because of their hard hearts and they would not glorify God in all that they were allowed to do by His grace and mercy. Therefore, let us commit ourselves to giving from the heart and not because we have to.