Numbers 35:28

For in the city of his refuge he shall dwell till the death of the great priest; and after the death of the great priest the slayer shall turn back to the land of his possession.

John 15:4-6

Remain in me, and I in you. As the branch cannot bear fruit of itself, if it remain not in the vine; so neither ye, if ye remain not in me.

Acts 11:23

Who, having been present, and seen the grace of God, rejoiced, and besought them all, with purpose of heart, to remain to the Lord.

Acts 27:31

Paul said to the centurion and to the soldiers, Except these should remain in the ship, ye cannot be saved.

Hebrews 3:14

For we have been partakers of Christ, if we hold the beginning of our foundation firm to the end;

Hebrews 6:4-8

For impossible for them once enlightened, and having tasted of the heavenly gift, and having partaken of the Holy Spirit,

Hebrews 9:11-12

And Christ being present, a chief priest of good things about to be, by a greater and more perfect tent, not made with hands, that is; not of this creation;

Hebrews 9:15-17

And for this he is mediator of a new covenant, that death having been, for redemption of the transgressions for the first covenant, the called might receive the promise of eternal inheritance.

Hebrews 10:26-30

For we sinning voluntarily after receiving the knowledge of the truth, there is left no more a sacrifice for sins,

Hebrews 10:39

And we are not of drawing down to perdition; but of faith to the acquisition of the soul.

Treasury of Scripture Knowledge

Summary

Because he should have remained in the city of his refuge until the death of the high priest: but after the death of the high priest the slayer shall return into the land of his possession.

After the death

Bible References

He should

John 15:4
Remain in me, and I in you. As the branch cannot bear fruit of itself, if it remain not in the vine; so neither ye, if ye remain not in me.
Acts 11:23
Who, having been present, and seen the grace of God, rejoiced, and besought them all, with purpose of heart, to remain to the Lord.
Acts 27:31
Paul said to the centurion and to the soldiers, Except these should remain in the ship, ye cannot be saved.
Hebrews 3:14
For we have been partakers of Christ, if we hold the beginning of our foundation firm to the end;
Hebrews 6:4
For impossible for them once enlightened, and having tasted of the heavenly gift, and having partaken of the Holy Spirit,
Hebrews 10:26
For we sinning voluntarily after receiving the knowledge of the truth, there is left no more a sacrifice for sins,

After the death

Hebrews 9:11
And Christ being present, a chief priest of good things about to be, by a greater and more perfect tent, not made with hands, that is; not of this creation;