Hebrews 3:15-19 King James Version (KJV)
15 While it is said, To day if ye will hear his voice, harden not your hearts, as in the provocation.
16 For some, when they had heard, did provoke: howbeit not all that came out of Egypt by Moses.
17 But with whom was he grieved forty years? was it not with them that had sinned, whose carcases fell in the wilderness?
18 And to whom sware he that they should not enter into his rest, but to them that believed not?
19 So we see that they could not enter in because of unbelief.
Hebrews 4:1 King James Version (KJV)
4 Let us therefore fear, lest, a promise being left us of entering into his rest, any of you should seem to come short of it.