As far back as the prophet Isaiah, God has identified how this New Testament rest would be distinguished:

"For with stammering lips and another tongue will He speak to this people. To whom He said, this is the rest by which you may cause the weary to rest, and this is the refreshing" (Isaiah 28:11-12).

Paul the Apostle identifies the New Testament experience of receiving the Holy Spirit (Acts 2:4,38), and the accompanying sign of speaking in tongues (Mark 16:17), as the basis of the rest, when he quotes the prophecy of Isaiah to the Corinthians (1 Corinthians 14:21) in connection with the operation of Spiritual Gifts, in particular, speaking in tongues.

To receive, or be baptised with, the Holy Spirit, we must first meet Yahuah's/God’s requirements of faith in the death and resurrection of Yahusha HaMashyach/Jesus Christ on our behalf, forsaking all attempts to gain any standing with Him by our own works, or keeping of a law. The Holy Spirit’s law, which is life in Mashyach Yahusha/Christ Jesus, sets us free from the custody of the law of sin and death (Romans 8:1-2).

So, being set free, we are finally able to keep a Sabbath of rest, in which, having ceased from our own works, as God did from His, we live in unity with God, remembering Him as our re-creator and sanctifier.

So the New Testament Sabbath is at last seen to be:

not a day of the week,

but the rest of a lifetime!