The Reign of Christ
Let's consider why it is that humans die and, what then is the hope of mankind?
Consider that the Bible tells us for 2,500 years "death reigned from Adam to Moses"(Rom.5:14). That means death existed before the Law was given to Israel, so its not of God's judgment. There's another cause of man's death entirely.
During this period of history it was clearly demonstrated in that had "death passed upon all men" (Rom 5:12). This death was not because the Law of Moses had condemned men to death, but rather... simply because they were the offspring of fallen Adam, possessing the same flesh of his loins, with his depraved Sin-nature in it. Just as genetic defects of a father may be passed onto his children physically, so it is that the Sin-infection in the flesh of Adam was passed to all mankind. Thus James wrote "... sin, when it is finished, bringeth forth death." (James 1:15)
Every person born since Adam bears the infection of "Sin" in their flesh body, and this brings for death to their bodies. Read carefully and consider what Paul wrote here below.
"We know that the Law is spiritual; but I Am A Creature Of The Flesh [Carnal, Unspiritual], Having Been Sold Into Slavery Under [The Control Of] Sin. 15 For I do not understand my own actions [I am baffled, bewildered]. I do not practice or accomplish what I wish, but I do the very thing that I loathe [which my moral instinct condemns]. 16 Now if I do [habitually] what is contrary to my desire, [that means that] I acknowledge and agree that the Law is good (morally excellent) and that I take sides with it. 17 However, it is no longer I who do the deed, but the sin [principle] which is at home in me and has possession of me. 18 For I know that nothing good dwells within me, that is, in my flesh. I can will what is right, but I cannot perform it. [I have the intention and urge to do what is right, but no power to carry it out.] 19 For I fail to practice the good deeds I desire to do, but the evil deeds that I do not desire to do are what I am [ever] doing. 20 Now if I do what I do not desire to do, it is no longer I doing it [it is not myself that acts], but The Sin [Principle] Which Dwells Within Me [Fixed And Operating In My Soul].
21 So I find it to be a law (rule of action of my being) that when I want to do what is right and good, evil is ever present with me and I am subject to its insistent demands. 22 For I endorse and delight in the Law of God in my inmost self [with my new nature]. 23 But I discern in my bodily members [in the sensitive appetites and wills of the flesh] a different law (rule of action) at war against the law of my mind (my reason) and making me a prisoner to the law of Sin That Dwells In My Bodily Organs [in the sensitive appetites and wills of the flesh]. (Romans 7:14-23 (AMP)
"... God sending his own Son in the likeness of sinful flesh, and for sin, condemned sin in the flesh: (Romans 8:3)
Then, it is that entirely apart from the Law that "Sin, when it is finished, bringeth forth death." (Jas.1:15).
Thus "death reigned from Adam to Moses, even over them that had NOT sinned after the similitude of Adam's transgression." Then also for 1,500 years, while under "the law," Sin continued to reign "unto death" (cf., Rom.5:20-21).
The reign of "Sin and death" had risen to its seeming pinnacle when Christ had was crucified. Israel had joined the Gentiles in declaring war on God and His anointed Son, This was prophesied in Psalm 2:1-3. Then, even after Jesus' resurrection His enemies stood by that awful deed. Saul of Tarsus was the leader of the continuing revolt when he consented to Stephen being stoned to death for His faith (cf., Acts 7). It was no longer merely a matter of sin; it was now continuing open rebellion in Israel.
But then this same Saul of Tarsus was saved by the ascended Christ from heaven (cf., Act 9) and he became "Paul, THE Apostle to the Gentiles (Rom 11:13). Paul was given to bear the word of the Lords "gospel of the grace of God" (Acts 20:24; cf., Eph 3:2) to be extended to all men.
Now by Paul's "gospel (good news) of the grace of God"... "Grace [Has] Reigned, through righteousness, unto eternal life, by Jesus Christ our Lord" (Rom 5:21).
For nearly 2,000 years, unto this day, we live under the reign of God's grace.
So, "Death Reigned from Adam to Moses" (Rom.5:14); just as Sin Reigned "unto death" after "the Law entered" (Vers.20-21)... But Now Grace Reigns.
GRACE REIGNS "through righteousness unto eternal life by Jesus Christ our Lord" (Rom 5:20-21). Thereby God offers all men salvation, free for the believing and receiving of Christ as their Savior.
Ultimately the Lord Jesus Christ will openly reign upon this earth (Rev 20:1-6) for 1,000 years, as King over Israel and the Gentile nations on earth.
The kingdom will then be delivered over to the Father (cf., 1Cor.15:24-28). Then, for all eternity the Father, Son and Holy Spirit will openly reign... in the person of Jesus Christ (cf., Rom.11:36).
"That in the dispensation of the fulness of times he (the Father) might gather together in one all things in (the person of) Christ, both which are in heaven, and which are on earth; even (that is) in him (Christ): (Ephesians 1:10)
We have the very real hope and expectation that one day, perhaps soon, we will be raised to "meet Him in the air" and then dwell with Him eternally in heaven (cf., 2Cor 5:1b). We need not be concerned for our death of the death of our loved ones who have received eternal salvation in Christ. We can be comforted knowing the truth.
"But I would not have you to be ignorant, brethren, concerning them which are asleep, that ye sorrow not, even as others which have no hope. 14 For if we believe that Jesus died and rose again, even so them also which sleep in Jesus will God bring with him. 15 For this we say unto you by the word of the Lord, that we which are alive and remain unto the coming of the Lord shall not prevent (go before) them which are asleep (have died). 16 For the Lord himself shall descend from heaven with a shout, with the voice of the archangel, and with the trump of God: and the dead in Christ shall rise first: 17 Then we which are alive and remain (unto His coming) shall be caught up together with them in the clouds, to meet the Lord in the air: and so shall we ever be with the Lord. 18 Wherefore comfort one another with these words." (1 Thessalonians 4:13-18)
I want to clarify the thought of some who may think that I'm saying the Lord had ceased to reign at one time. No! The fact is that from eternity past, and from Adam to this present day, the Sovereign Lord has always been "on the throne." He has been orchestrating and arranging the redemption of mankind through Christ, "while we were yet sinners" (Rom 5:8). Rather than ruling directly, He has intervened and overruled in the affairs of men (to whom he gave free wills) to offer all men the free gift of salvation "by grace through faith" in Christ alone.
"For by grace are ye saved through faith; and that not of yourselves: it is the gift of God: 9 Not of works, lest any man should boast." (Ephesians 2:8-9)