Paul here in Hebrews 4:4-11 is quoting David from Psalms 95:10-11:
Hebrews 4:4-11 (KJV)
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. And in this place again, If they shall enter into my rest. Seeing therefore it remaineth that some must enter therein, and they to whom it was first preached entered not in because of unbelief: Again, he limiteth a certain day, saying in David, To day, after so long a time; as it is said, To day if ye will hear his voice, harden not your hearts. For if Jesus had given them rest, then would he not afterward have spoken of another day. There remaineth therefore a rest to the people of God. For he that is entered into his rest, he also hath ceased from his own works, as God did from his. Let us labour therefore to enter into that rest, lest any man fall after the same example of unbelief.
and here is Psalms 95:10-11:
Psalms 95:10-11 (KJV)
Forty years long was I grieved with this generation, and said, It is a people that do err in their heart, and they have not known my ways: Unto whom I sware in my wrath that they should not enter into my rest.
Notice the word "rest" here? it is in reference to the land of Canaan, or the "promise land", it is well known to those then that the promise land was like a heavenly place...
Just because the word rest appears, that does not mean it negates anything. Let's read a little about the people who do err in their heart...
Deu 5:29 O that there were such an heart in them, that they would fear me, and keep all my commandments always, that it might be well with them, and with their children for ever!
Here is how they erred, the hardness of their heart prevented them from obeying the Commandments in the manner God intended. How did He intend?
This is what Mat 5, 6 and 7 is about. The heart. Obeying God in thought and deed, not grudgingly, but with "joy and gladness".
But because of the peoples disobedience to God, NONE of them but TWO ever entered, Joshua and Caleb...
Do you realize what you wrote there? Because they disobeyed the Law of God! Same principle is reiterated in Heb 8...
Heb 8:8
For finding fault with them, he saith, Behold, the days come, saith the Lord, when I will make a new covenant with the house of Israel and with the house of Judah:
The problem was not the Law or even the Covenant, the problem was with the people. They erred in their heart, the did not have the heart to obey God as we have already seen.
Paul is telling the Jews here in Heb. 4:4-11 that if they are not obedient to God they will not enter his "heavenly rest", just like those that he lead out of the land of Egypt...
Exactly! Let's use another example, no matter how much you love someone and wish them well and try to do good for them, yet you steal their possessions, have you disobeyed? Now matter how much we proclaim we love God, say we want to serve Him and His people, if we disobey Him, what have we done? Righteousness? Disobedience brings wrath...
Eph 5:1 Be ye therefore followers of God, as dear children;
Eph 5:2 And walk in love, as Christ also hath loved us, and hath given himself for us an offering and a sacrifice to God for a sweetsmelling savour.
Eph 5:3 But fornication, and all uncleanness, or covetousness, let it not be once named among you, as becometh saints;
Eph 5:4 Neither filthiness, nor foolish talking, nor jesting, which are not convenient: but rather giving of thanks.
Eph 5:5 For this ye know, that no whoremonger, nor unclean person, nor covetous man, who is an idolater, hath any inheritance in the kingdom of Christ and of God.
Eph 5:6 Let no man deceive you with vain words: for because of these things cometh the wrath of God upon the children of disobedience.
Col 3:5 Mortify therefore your members which are upon the earth; fornication, uncleanness, inordinate affection, evil concupiscence, and covetousness, which is idolatry:
Col 3:6 For which things' sake the wrath of God cometh on the children of disobedience:
Col 3:7 In the which ye also walked some time, when ye lived in them.
Col 3:8 But now ye also put off all these; anger, wrath, malice, blasphemy, filthy communication out of your mouth.
Heb 2:1 Therefore we ought to give the more earnest heed to the things which we have heard, lest at any time we should let them slip.
Heb 2:2 For if the word spoken by angels was stedfast, and every transgression and disobedience received a just recompence of reward;
Heb 2:3 How shall we escape, if we neglect so great salvation; which at the first began to be spoken by the Lord, and was confirmed unto us by them that heard him;
The Greek unless you completely understand it will only confuse you and lead you astray, you cannot always arrive to the meaning of a Greek word by its root... it is a reflective language and endings and many other things can completely change the meaning of the word...
There is a complete difference in the words used for rest in Heb 4...
Verse 4...
G2664
καταπαύω
katapauō
kat-ap-ow'-o
From G2596 and G3973; to settle down, that is, (literally) to colonize, or (figuratively) to (cause to) desist: - cease, (give) rest (-rain).
verse 5...
G2663
κατάπαυσις
katapausis
kat-ap'-ow-sis
From G2664; reposing down, that is, (by Hebraism) abode: - rest.
finally, verse 9
G4520
σαββατισμός
sabbatismos
sab-bat-is-mos'
From a derivative of G4521; a “sabbatismâ€, that is, (figuratively) the repose of Christianity (as a type of heaven): - rest.
A Sabbatism, it is a derivative of 4521...
G4521
σάββατον
sabbaton
sab'-bat-on
Of Hebrew origin [H7676]; the Sabbath (that is, Shabbath), or day of weekly repose from secular avocations (also the observance or institution itself); by extension a se'nnight, that is, the interval between two Sabbaths; likewise the plural in all the above applications: - sabbath (day), week.
He is referring to "heavenly rest" in Heb. 4:11 like David is referring to "heavenly rest" in Psalms 95:11
You are missing the point...
The Sabbath rest is a Commandment and also a shadow or type of the Millenium.
Col 2:17 Which are a shadow of things to come; but the body is of Christ.
Things to come, yet future.
As far as them not entering into that rest...
They couldn't because of the hardness of their hearts prevented them from obeying.