When God rested on the 7th day, there was no sin in the world (prior to the fall).

Now, after the fall, sin came to be.

Hence, Lord Jesus Christ reveals a ‘secret’ that the Father has ‘always’ been working ‘to this day’ (the Father has left the Sabbath because there’s work to be done —> due to sin).

Read the verses below to see this ‘literally’ even as Christ the Lord demonstrates this point to the jews by ‘breaking’ the Sabbath instead:

“So, because Jesus was doing these things on the Sabbath, the Jewish leaders began to persecute Him. In His defense Jesus said to them, “My Father is always at His work to this very day, and I too am working.” For this reason they tried all the more to kill Him; not only was He breaking the Sabbath, but He was even calling God His own Father, making Himself equal to God.” (John 5:16 – 18)

In the age/ages which are coming, there is ‘another Sabbath’ (which will be a rest as the problem of sin gets ‘solved’ via universal reconciliation in Christ).

Thus the verse below clearly states that this Sabbath is “another day” (not the current earthly Sabbath day of the Old Covenant) but most likely pertaining to the age-during life which the ‘people of God’ will enjoy in their ‘rest’ during the ‘next age’:

“For if Joshua had given them rest, God would not have spoken later about another day. There remains, then, a Sabbath-rest for the people of God;” (Hebrews 4:8 – 9)

P/S:
The author of Hebrews is ‘not’ writing the verse above to mean your “Sunday attendance at church” (Read this chapter carefully; that’s not the topic which is discussed here).

Quote verses in truth.