Hebrews 4 speaks of two rests. The Gospel and the Sabbath. One can not keep the Sabbath unless they are experiencing the Gospel.
1 Let us therefore fear, lest, a promise being left us of entering into his rest, any of you should seem to come short of it.
The Rest, His Rest here is the Gospel. This is reiterated in the next verse.
2.For unto us was the Gospel preached , as well as unto them: but the word preached did not profit them, not being mixed with faith in them that heard it.
The Gospel which is the New Covenant, the placing of God's commandments, His Word, His intent into our hearts and minds through the indwelling of His Spirit. This is the rest in verse 1 which we enter into through faith. Or do not enter into because of unbelief (obstinate and rebellious disobedience).
This unbelief is discussed earlier in chapter 3
Hebrews
3:6 But Christ as a son over his own house; whose house are we, if we hold fast the confidence and the rejoicing of the hope firm unto the end.
3:7 Wherefore (as the Holy Ghost saith, To day, [now] if ye will hear his voice,......
8 Harden not your hearts,......
11 So I sware in my wrath, They shall not enter into my rest.
12 Take heed, brethren, lest there be in any of you an evil heart of unbelief, in departing from the living God.
13 But exhort one another daily, while it is called To day; lest any of you be hardened through the deceitfulness of sin. For they do alway err in their heart; and they have not known my ways.
14 For we are made partakers of Christ, (his indwelling Spirit) if we hold the beginning of our confidence stedfast unto the end;
15 While it is said, To day if ye will hear his voice, harden not your hearts, as in the provocation.
16 For some, when they had heard, did provoke: howbeit not all that came out of Egypt by Moses.
17 But with whom was he grieved forty years? [was it] not with them that had sinned,
Through an Evil heart of unbelief, we depart from the living God, hardened through the deceitfulness of sin we will not know His ways.
So today hear his voice, harden not your hearts, as in the provocation when they did provoke. Them that sinned, evil hearted unbelievers, hardened through the deceitfulness of sin. Which whom was He grieved? Them that sinned and had not held their confidence steadfast unto the end. These are those who had not entered into His Rest therefore had never kept a Sabbath
Now Back to chapter 4:1,2
Let us therefore fear, lest, a promise being left [us] of entering into his rest, any of you should seem to come short of it. For unto us was the gospel preached, as well as unto them: but the word preached did not profit them, not being mixed with faith in them that heard [it]4:3 For we which have believed, do enter into rest.
We do enter into His Rest, receive the Gospel the New Covenant, Which is His Commandments, His Word in our Hearts and in our minds. The anointing; Christ in us the Hope of Glory. For it is He that worketh in us to will and do His good pleasure. Not that we are sufficient of ourselves to think anything as of ourselves; but our sufficiency is of God.
2 Cor. 3:5 Heb 8:10
vs. 3 As he said, As I have sworn in my wrath, if they shall enter into my rest: although the works were finished from the foundation of the world.
This rest is still speaking of the Gospel. The works for our salvation in the Gospel were finished from beginning when He had laid the foundation of the World.
We trampled on the gift of the Gospel from the Beginning of time and even though we deserve God's wrath salvation is still available to us.
According as he hath chosen us in him before the foundation of the world, that we should be holy and without blame before him in love..... the Lamb slain from the foundation of the world.
Rev 13:8; Eph 1:4
Now pay attention please.
4 For he spake in a certain place of the seventh day on this wise, And God did rest the seventh day from all his works. 5 And in this again, If they shall enter into my rest.
And this again, the Sabbath, the Seventh Day if we enter into, receive His rest, the Gospel, the indwelling of His Spirit.
For God spoke of the Seventh Day in a certain place and that certain place was on Mt Sinia.
And this again he speaks it says in verse 4 and 5, "if we shall enter into His Rest," receive the Gospel.
6.Seeing therefore (because) it remaineth that some must enter therein (the Gospel), and they to whom it was first preached entered not in because of unbelief:
Remember the previous chapter? They Never received the Gospel therefore since they never truly enter into union with the Father they never truly kept a Sabbath. They could not due to their unbelief through the deceitfulness of sin.
A unholy being cannot keep a day holy, sanctified. Their very presence defiles it.
So they never truly kept the Sabbath. They were defiled by the deceitfulness of sin. We are enjoined to rest and to keep the day Holy. If we have iniquity on our hearts it prevents us from keeping it Holy. Therefore they never truly kept it in the way our Lord YHWH had intended.
7.Again, he limiteth a certain day, saying in David [Ps 95:7,8] To day, [ Now ]after so long a time; as it is said , To day [Right now] if ye will hear his voice, harden not your hearts as in the day of provocation, 8.For if Jesus had given them rest , [Joshua leading the children of Israel into the promised land] , then would he, David, [See Psalm 95] not afterward have spoken of another day.
Verses six through eight are a call to repentance. Today (in other words now) after so long a time today (right now) if you will hear His voice harden not your hearts. Receive the rest that we receive in Christ, the Gospel. For He is our God and we are the people of His Pasture, His Resting, His indwelling; for we are the temple of the living God; as God hath said, I will dwell in them and walk in them Heb 8:10 I will put my laws into their mind and write them in their hearts and I will be their God and they shall be my people.That is the Gospel; the New Covenant.
9.There remaineth therefore a rest to the people of God.
As you know The Greek word here in verse 9 for rest means a "sabbathing", a keeping of a Sabbath. Prior to this the Greek word used for rest meant to rest, to stop. That is why it was used in relation to the Gospel. God wants us to stop living our lives in sin; the unbelief (obstinate and rebellious disobedience) spoken of and live our lives in Him. Rest in Him. His Rest, the Gospel. For it is He that wants to work in you both to will and do His good pleasure.
10.For he that is entered into his rest [received the Gospel. Which by the way enables us to be Holy and remain so, through His indwelling Spirit ], he also hath ceased from his own works, as God did from His.
Did you get that? Because of receiving the Gospel we cease from our own works as GOD did from His.
"As is" is a direct comparison. So with that you must ask yourself how and when did God cease from his own works. The answer to that is recorded in Gen 2.... on the Seventh Day, And God did rest from all His work on the seventh day (see Hebrews Verse 4 and Genesis Chapter 2:1-3).
God Is a Spiritual Being he is always in the state of Spiritual Rest . HE did not enter into the Gospel; the Spiritual Rest to which we are called. On the Seventh Day Sabbath he ceased from the physical labor of creation. Which is recorded in Genesis 2.
Therefore He that receives the Gospel, will cease from their own physical work as God did from His physical work on the 7th day Sabbath. And this is, was and will continue to be done on the Seventh day of the week into eternity.
And it shall come to pass, that from one new moon to another, and from one sabbath to another, shall all flesh come to worship before me, saith the LORD.
(Isa 66:23 KJV)