How old was Cain when he murdered Abel?
The answer is not revealed in Scripture, but the probable point of the question is that the common assumption may not be accurate. Most seem to assume that Cain and Abel were boys in their teens or early twenties.
From the narrative, it seems Cain was married when he went from the presence of the Lord (Gen 4:16, 17). Judging from the age at which the men in the following chapter had sons, Cain would have been considerably older than twenty.
In addition, Adam was 130 years old (5:3) at the birth of Seth, who was “another seed instead of Abel” (4:25). It was as if family life began all over again at that point.
We do not know how long Adam lived in the Garden of Eden. We do know that, unlike all his posterity, he had mature manhood and was capable of parenthood from his first breath. Judging from Satan’s delight to attack all that brings pleasure to God’s heart (see Matthew 3:17 and 4:1, particularly), his attack in Eden did not happen after many years.
Cain and Abel were born after Adam was expelled from Eden (Gen 4:1), so a considerable amount of time could have elapsed between the births of Cain and Abel and the birth of Seth.
The reference in 1 John 3:12 speaks of Cain’s works and of Abel’s. This suggests a background to the narrative of the two offerings recorded in Genesis 4.
Although we cannot be certain of Cain’s age when he slew Abel, the relevant evidence indicates that “the way of Cain” (Jude 11) was well initiated before the events of Genesis 4:3-16.
Will believers and unbelievers die in the Millennial reign?
All who enter the Millennial reign of the Lord Jesus will be believers (Matt 13:41-42). The provisions of the New (Jer 31:31) or Everlasting (32:40) Covenant with Israel will produce in those believers a new heart and inward submission to God’s moral law (31:33). God promises, “I will put My Spirit within you, and cause you to walk in My statutes” (Eze 36:27). In an environment where the devil is inactive (Rev 20:2,3) and the world encourages and supports this inward bent of the believers, the effect will be remarkable. This does not mean these believers will not sin, for they will still have the flesh within as we do in this age. Nonetheless, they will obey from their hearts the glorious King.
In contrast, a person born during the Millennium will be “born of the flesh” (John 3:6) and, unless converted, will obey only externally. He may cover his rebellion for 100 years, but, when the rebellion of his heart flares into action, “the sinner being an hundred years old shall be accursed” (Isa 65:20).
Justice will be perfect during this time (Isa 11:2-5) and the punishment will fit the crime. Those who refuse to acknowledge their indebtedness to the Lord for their harvest will suffer drought on their next planting (Zech 14:16-19). Therefore, the Lord will not punish every sin with death. The degree of sin which He punishes with death would appear to be blatant acts of rebellion, likely including a rival worship to that of the living God.
Unbelievers are capable of such rebellion during this period; in fact, a great multitude will rebel when Satan is freed at the close of the thousand years (Rev 20:7-9). The blessings of the New Covenant will most likely preserve believers from such rebellion (“I will also save you from all your uncleannesses: . . . and lay no famine upon you” Eze 36:29, see also Rom 11:26, 27).
Apparently, therefore, the judgment of death will fall on unbelievers, but not believers during the Millennium.
Do worshippers offer animal sacrifices during the Millennial reign?
Yes. At the end of Ezekiel 39, God speaks of gathering His people from the lands of their enemies and pouring out His Spirit on them (vv 25-29). The last nine chapters, from 40 to 48, picture the Millennial temple and city. Seven of those nine chapters refer to offerings and to the priests who offer them. The city and the temple are literal, for the rebuilding of the city (40:2-3) and the return of the glory of God (43:2) are linked with the literal destruction of the city (40:1) and the departure of God’s glory (43:3). Therefore we must also interpret the priests and the sacrifices literally.
Which of the offerings will be offered? (Zechariah 14:21)
The last nine chapters of Ezekiel include references to all five of the major offerings. The sin offering is mentioned 14 times, the trespass offering four times. Eighteen times Ezekiel refers to the burnt offering(s), and 14 times to the meal offering(s). “The sacrifice” is mentioned three times, twice in conjunction with the burnt offering; the other time the priests are boiling it – not burning it – in preparation for eating. This would refer to the peace offering.
Why will these animal sacrifices be required?
The New Testament makes it clear that the offerings under the Old Covenant anticipated the once-for-all sacrifice of Christ, but they did not satisfy God’s requirements (Heb 10: 1-12) nor bring rest to the offerer. The sacrifice of Christ completely satisfied God’s requirements and ended the need of these typical sacrifices. Further, the New Testament shows that righteous living was not dependent on a legal system which included the offering of sacrifices (Gal 3:2, 3, 5). Therefore the sacrifices in the Millennium will not anticipate the sacrifice, for it is completed. They will not be typical, for the types are fulfilled in “the offering of the body of Jesus Christ once for all” (Heb 10:10). Neither will they contribute to righteous living.
Those offerings will be a visible reminder of the infinite sacrifice that has brought such blessing to believers of every age, to the nation of Israel and to the nations, to the Church, to the entire creation, and to the ages of the ages. “To Him be glory both now and forever. Amen” (2Pe 3:18)!