And if they do not persist in unbelief, they will be grafted in, for God is able to graft them in again.
NIV
And even those others [the fallen branches, Jews], if they do not persist in [clinging to] their unbelief, will be grafted in, for God has the power to graft them in again.
AMP
And they also, if they abide not still in unbelief, shall be graffed in: for God is able to graff them in again.
KJV
So we see that they were not able to enter, because of their unbelief.
NIV
So we see that they were not able to enter [into His rest], because of their unwillingness to adhere to and trust in and rely on God [unbelief had shut them out]. [Num. 14:1-35.]AMP
So we see that they could not enter in because of unbelief.
KJV
Yet he did not waver through unbelief regarding the promise of God, but was strengthened in his faith and gave glory to God,
NIV
No unbelief or distrust made him waver (doubtingly question) concerning the promise of God, but he grew strong and was empowered by faith as he gave praise and glory to God,
AMP
He staggered not at the promise of God through unbelief; but was strong in faith, giving glory to God;
KJV
What if some were unfaithful? Will their unfaithfulness nullify God's faithfulness?
NIV
What if some did not believe and were without faith? Does their lack of faith and their faithlessness nullify and make ineffective and void the faithfulness of God and His fidelity [to His Word]?
AMP
For what if some did not believe? shall their unbelief make the faith of God without effect?
KJV
Let us, therefore, make every effort to enter that rest, so that no one will perish by following their example of disobedience.
NIV
Let us therefore be zealous and exert ourselves and strive diligently to enter that rest [of God, to know and experience it for ourselves], that no one may fall or perish by the same kind of unbelief and disobedience [into which those in the wilderness fell].
AMP
Let us labour therefore to enter into that rest, lest any man fall after the same example of unbelief.
KJV