For if Joshua had given them rest, then would he not afterward have spoken of another day (Hebrews 4:8).
The reference above belongs to the exhortation by the writer of Hebrews concerning the rest promised for the people of God. In chapter 3, he tells us how the people of Israel fell in the wilderness because of unbelief.
God became so angry with the Israelites in the wilderness that He swore in His wrath that that generation would not enter into His rest, i.e., the Promised Land.
The author of Hebrews, writing to Hebrew believers speaks of Israel’s land inheritance as a rest foreshadowing the true rest which was yet to come.
Notice that he says, “IF JOSHUA HAD GIVEN THEM REST, he would not have spoken of another day.”
Israel never entered into God’s rest under Joshua, though they inhabited the land. This is why he mentions “another day” and quotes the words of David from Psalms 95 which was said by David, long after Israel occupied the land.
Again, he limiteth a certain day, saying in David, To day, after so long a time; as it is said, Today if ye will hear his voice, harden not your hearts (Hebrews 4:7).
Hebrews 4:6-7 in New Living Translation says the following.
God’s rest is there for people to enter, but those who first heard this good news failed to enter because they disobeyed God. SO GOD SET ANOTHER TIME FOR ENTERING HIS REST, and that time is today. God announced this through David much later in the words already quoted: “Today when you hear his voice, don’t harden your hearts.” Now if Joshua had succeeded in giving them this rest, God would not have spoken about another day of rest still to come.
Writing to Hebrew believers, the writer of Hebrews tells them that there remains a rest to be entered by the people of God. That rest is the finished work of Christ. The author of Hebrews will continue to expound on this truth throughout the epistle as he expounds on Jesus’ Priesthood, sacrifice, and the new covenant of which Christ is the mediator.
Israel’s inheritance in the land of Canaan wasn’t a permanent rest. Instead, it was only a type and a foreshadowing of something much more significant: the true rest that comes through faith in Jesus.