New Defender's Study Bible Notes
4:3 process of time. Literally, “at the end of the days,” undoubtedly a reference to the “seventh day,” which God had hallowed as a day of rest and blessing (Genesis 2:3). On such a day, men would follow God’s example in ceasing from their regular labors in order to have fellowship with God, possibly meeting with Him at the entrance to Eden (Genesis 3:24).
4:3 an offering. Such fellowship, however, required that worshipers approach God with an offering that would make them suitable for His presence. Adam and Eve no doubt had instructed their sons that this required a substitutionary sacrifice of innocent blood (Genesis 3:21). Cain, however, chose to bring another type of offering on this occasion.
4:4 Abel. Abel was a man of faith, the first listed in the chapter of faith (Hebrews 11). Since he brought a “by faith...a more excellent sacrifice” (Hebrews 11:4), it is evident that God had given instruction concerning the sacrifice, which Abel believed and obeyed. The Lord Jesus described him as “righteous” (Matthew 23:35) and even as one of God’s prophets (Luke 11:50,51).
4:5 his countenance fell. Cain’s anger reflects pride in his own works which, because of that very fact, God regarded as “evil” (I John 3:12).