Philoxenus of Mabbug

And moreover, we may also see simplicity in Abel, and the Holy Book sheweth us that he was more simple than Cain; for they both brought offerings to the Lord, and the offering of simplicity was accepted, but the offering of wickedness was rejected. And Cain was angry with the Lord and with Abel; with Abel because he envied him, and with the Lord because He had rejected his offering. If he had been of a simple disposition he would not have been envious, and if he had been sincere he would not have been angry with the Lord.