Peace be with you and yes, it is for unbelievers and they may be consist also of Christian believers, who have not welcomed the Gospels. They are not Helped by the HOLY SPIRIT, who teaches and they are also 'ever learning but never come into the knowledge of Truth'.
Until today or whenever, there will be only the given New Testament by our 'author and finisher of our faith' and who have gone away to a far away land to be crown as King of kings'. Initially this was established by GOD the FATHER of our LORD JESUS CHRIST, even to the shedding of many innocent blood.
We can consider them in a simple way, kind of similar to a worldly contract method but this is of GOD made with all redeemed mankind through HIS SON and the HOLY SPIRIT. They were called, when struggling and in helplessness and hopelessness. They are those who have come to believe and have accepted all that is written in the contract, the 'terms and conditions'/'rules and regulations' which also calls them all to 'abide' in order to 'bear fruits'. .
Apart from staying faithful to all of these things in the New Covenant, from time to time, generations after generations that are also quoted to be 'difficult to follow' by our MESSIAH Himself and further more quoted that towards the end 'many will give up their faith and start hating each other', then one may 'have accepted another Christ and another spirit'.
