Hebrews 3:19

From Hebrews 3, in the Book of Hebrews (New Testament).

Read in Context

But with whom was he grieved forty years? was it not with them that had sinned, whose carcases fell in the wilderness?

And to whom sware he that they should not enter into his rest, but to them that believed not?

So we see that they could not enter in because of unbelief.