Hebrews points to the sabbath as the rest that believers may enter into. John used “a thousand years” as a symbol of the sabbath day, the rest day of God’s creation.
The thousand year reign and the sabbath rest
What is the symbolic meaning of the thousand years in Revelation 20:4, when Satan is bound, and the saints reign with Christ?
Hebrews 4:8-9 says that there is a rest remaining for the people of God, which is related to the land of promise, called a rest in Joshua 1:13, and also to the seventh day of creation, when God rested.
When John referred to the first resurrection, he meant the resurrection of Jesus, who was raised up from the grave. Those who reign with him are “translated into his kingdom.” Paul wrote:
Giving thanks unto the Father, which hath made us meet to be partakers of the inheritance of the saints in light:
Who hath delivered us from the power of darkness, and hath translated us into the kingdom of his dear Son:
In whom we have redemption through his blood, even the forgiveness of sins:
Who is the image of the invisible God, the firstborn of every creature:
Paul said believers are “risen with him.”
And ye are complete in him, which is the head of all principality and power:
In whom also ye are circumcised with the circumcision made without hands, in putting off the body of the sins of the flesh by the circumcision of Christ:
Buried with him in baptism, wherein also ye are risen with him through the faith of the operation of God, who hath raised him from the dead.
Paul said the saints have become “a new creature.” [2 Corinthians 5:17] He said God has “raised us up together, and made us sit together in heavenly places in Christ Jesus.” [Ephesians 2:6]
Henry Alford, when discussing Revelation 20:5, rejected the idea that the first resurrection in Revelation 20 applies to the saints reigning in this present life. He wrote: 
It will have been long ago anticipated by the readers of this Commentary, that I cannot consent to distort words from their plain sense and chronological place in the prophecy, on account of any considerations of difficulty, or any risk of abuses which the doctrine of the millennium may bring with it. Those who lived next to the Apostles, and the whole Church for 300 years, understood them in the plain literal sense: and it is a strange sight in these days to see expositors who are among the first in reverence of antiquity, complacently casting aside the most cogent instance of consensus which primitive antiquity presents.
As regards the text itself, no legitimate treatment of it will extort what is known as the spiritual interpretation now in fashion. If, in a passage where two resurrections are mentioned, where certain “souls lived” at the first, and the rest of the “dead lived” only at the end of a specified period after that first,–if in such a passage the first resurrection may be understood to mean spiritual rising with Christ, while the second means literalrising from the grave; –then there is an end of all significance in language, and Scripture is wiped out as a definite testimony to any thing. If the first resurrection is spiritual, then so is the second, which I suppose none will be hardly enough to maintain: but if the second is literal, then so is the first, which in common with the whole primitive Church and many of the best modern expositors, I do maintain, and receive as an article of faith and hope.
Alford’s comments seem to ignore the priority of the resurrection of Jesus, who is “the firstborn of every creature,” and “the firstborn from the dead,” [Colossians 1:18] so his resurrection was the first resurrection. When John said, “This is the first resurrection” in verse 5, he referred to the resurrection of Jesus.
Those who have a part in the first resurrection, John said, are those who were “beheaded for the witness of Jesus, and for the word of God.” This alludes to the saints as a “living sacrifice.” [Romans 12:1]
But why does John say the reign of the saints is for a thousand years? This number suggests completeness, and perhaps, the “abundant life,” that Jesus promised, when he said, “I am come that they might have life, and that they might have it more abundantly.” [John 10:10]
The apostle Peter said, “But, beloved, be not ignorant of this one thing, that one day is with the Lord as a thousand years, and a thousand years as one day.” [2 Peter 3:8]
In Exodus 20:11, everything is said to have been made in six days, but on the seventh day God rested. Hebrews points to the sabbath as the rest that believers may enter into. John used “a thousand years” as a symbol of the sabbath day, the rest day of God’s creation.
John said that they “had not worshipped the beast, neither his image, neither had received his mark upon their foreheads, or in their hands; and they lived and reigned with Christ a thousand years.” Thus, the thousand years has to do with the saints reigning with Christ. It is foreshadowed by the rest of the seventh day of creation. This is supported in Revelation 14:11, where John says those who worship the beast, or receive his mark, “have no rest day nor night.” And he adds, “Here is the patience of the saints: here are they that keep the commandments of God, and the faith of Jesus.” [vs. 12]