Hebrews 3:19
"So we see that they could not enter in because of unbelief."
Cross References (ranked by relevance)
I will therefore put you in remembrance, though ye once knew this, how that the Lord, having saved the people out of the land of Egypt, afterward destroyed them that believed not.
He that believeth on the Son hath everlasting life: and he that believeth not the Son shall not see life; but the wrath of God abideth on him.
He that believeth on him is not condemned: but he that believeth not is condemned already, because he hath not believed in the name of the only begotten Son of God.
He that believeth and is baptized shall be saved; but he that believeth not shall be damned.
That they all might be damned who believed not the truth, but had pleasure in unrighteousness.