What exactly is His rest?
Let's look at Hebrews 4:
'For we who have believed enter that rest, just as He has said, "AS I SWORE IN MY WRATH, THEY SHALL NOT ENTER MY REST," although His works were finished from the foundation of the world. For He has said somewhere concerning the seventh day: "AND GOD RESTED ON THE SEVENTH DAY FROM ALL HIS WORKS"; and again in this passage, "THEY SHALL NOT ENTER MY REST." Therefore, since it remains for some to enter it, and those who formerly had good news preached to them failed to enter because of disobedience, He again fixes a certain day, "Today," saying through David after so long a time just as has been said before, "TODAY IF YOU HEAR HIS VOICE, DO NOT HARDEN YOUR HEARTS."
'For if Joshua had given them rest, He would not have spoken of another day after that. So there remains a Sabbath rest for the people of God. For the one who has entered His rest has himself also rested from his works, as God did from His. Therefore let us be diligent to enter that rest, so that no one will fall, through following the same example of disobedience.' [Hebrews 4:3-11]
This passage states that His works were finished from the foundation of the world...and we know that His Word is settled forever. [Psalm 119:89]
His finished works are His forever settled Word!
Everything God did He did by His Word...and that is settled forever, eternally. The Hebrew word 'forever' is owlam—continuous existence, perpetual, everlasting, eternal.
And we know that 2 Corinthians 1:20 tells us 'For as many as are the promises of God, in Him they are YES; therefore also through Him is our Amen to the glory of God through us.'
And The Point Is...
The point is, His forever settled Word, His everlasting promises are His rest, and they belong to us. Just as the Promised Land was His rest for the Israelites [Hebrews 3:16-19] so His forever settled Word is our rest.
Consider Hebrews 3:18-19; 4:2...
'And to whom did He swear that they would not enter His rest, but to those who were disobedient? So we see that they were not able to enter because of unbelief.
'For indeed we have had good news preached to us, just as they also; but the word they heard DID NOT PROFIT THEM, because IT WAS NOT UNITED BY FAITH IN THOSE WHO HEARD.'
Israel did not enter the rest of His promised land because of unbelief...they believed the evil report of the 10 spies instead of the faith-filled report of Joshua and Caleb. [Numbers 13]
God had promised them the land! But they did not unite that word, that promise, with faith, so the promise did them no good. They did not enter the promised rest.
What was that rest? Peace...
'Then it shall come about when the LORD your God brings you into the land which He swore to your fathers, Abraham, Isaac and Jacob, to give you, great and splendid cities which you did not build, and houses full of all good things which you did not fill, and hewn cisterns which you did not dig, vineyards and olive trees which you did not plant, and you eat and are satisfied, then watch yourself, that you do not forget the LORD who brought you from the land of Egypt, out of the house of slavery.' [Deuteronomy 6:10-12]
You cannot have peace without wealth, health and protection. And every one of His promises, including those of health, wealth and protection are our promised land.
Jesus prayed "Your will be done on earth as it is in heaven" [Matthew 6:10] so we know that these promises are for this earthly, natural life.
His Word is His work, His rest. Enter in by uniting it by faith.