Hebrews 4:9-10 - anyone who enters God's rest also rests from his own work

There remains, then, a Sabbath-rest for the people of God; for anyone who enters God's rest also rests from his own work, just as God did from his.

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.

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.

Hebrews 4:9-10

Commentary

Here the writer uses a different Greek word for rest (sabbatismos), which is related to the word Sabbath. It refers to the eternal rest which will be enjoyed by all who have been redeemed by the precious blood of Christ. It is a "Sabbath" keeping that will never end.
Whoever enters God's rest enjoys a cessation from labor, just as God did on the seventh day. Before we were saved, we may have tried to work for our salvation. When we realized that Christ had finished the work at Calvary, we abandoned our own worthless efforts and trusted the risen Redeemer. After salvation, we expend ourselves in loving toil for the One who loved us and gave Himself for us. Our good works are the fruit of the indwelling Holy Spirit. We are often weary in His service, though not weary of it. In God's eternal rest, we shall cease from our labors down here. This does not mean that we will be inactive in heaven. We shall still worship and serve Him, but there will be no fatigue, distress, persecution, or affliction.

MacDonald, W., & Farstad, A. (1997, c1995). Believer's Bible Commentary : Old and New Testaments (Heb 4:9). Nashville: Thomas Nelson.

Hebrews 13:5 - be content with what you have

Keep your lives free from the love of money and be content with what you have, because God has said, "Never will I leave you; never will I forsake you."

Let your conversation be without covetousness; and be content with such things as ye have: for he hath said, I will never leave thee, nor forsake thee.

Make sure that your character is free from the love of money, being content with what you have; for He Himself has said, "I WILL NEVER DESERT YOU, NOR WILL I EVER FORSAKE YOU,"

Hebrews 13:5

Commentary

Those tempted by the love of money and discontent are particularly people who seek their security in financial resources (Matt. 6:19-21, 24-34). But God's promise to stay with Joshua gives greater confidence: "I will not leave you nor forsake you" (Josh. 1:5). Our confident response reaffirms that the Lord our helper (2:18; 4:16) sets us free from all kinds of fear (2:15; 11:23, 27).

Whitlock, L. G., Sproul, R. C., Waltke, B. K., & Silva, M. (1995). Reformation study Bible, the : Bringing the light of the Reformation to Scripture : New King James Version. Includes index. (Heb 13:5). Nashville: T. Nelson.

"I will never leave you nor forsake you"
This quotation is one of the most emphatic statements in the NT. In Greek it contains two double negatives, similar to saying in English, " I will never, ever, ever forsake you." Jesus uses the same technique to express the certainty of eternal life for believers (John 10:28).

Radmacher, E. D., Allen, R. B., & House, H. W. (1999). Nelson's new illustrated Bible commentary (Heb 13:5-6). Nashville: T. Nelson Publishers.