Influenced by certain Enlightenment assumptions, we like to believe that we all may reserve the right to not believe certain things. But in Scripture to “believe not” is described as a sin. The verb used to describe this unbelief in Scripture is apisteo.
The male disciples had been told by Jesus that He was going to come back from the dead, and then when He did, and the women testified that they had seen Him, refused to believe anyway. “And they, when they had heard that he was alive, and had been seen of her, believed not”(Mk 16:11). “And their words seemed to them as idle tales, and they believed them not”(Lk 24:11). Of course they were eventually persuaded, and their shock at that time is described in a figure of speech that was not sinful. They believed not “for joy” (Luke 24:41)
Jesus tells His disciples that the message they were to preach to the nations was a winnowing message. “He that believeth and is baptized shall be saved; but he that believeth not shall be damned”(Mk 16:16). And this is how the message has worked from the first century until now. Some who hear believe, and others do not. “And some believed the things which were spoken, and some believed not” (Ac 28:24).
God is not thrown down from His throne by unbelief. How could that be? “For what if some did not believe? shall their unbelief make the faith of God without effect?”(Ro 3:3). God will work out His good purposes regardless of the unbelief shown by the ultimate rebels, and He will work over, around, through, and into the temporary unbelief of His weak children. “If we believe not, yet he abideth faithful: he cannot deny himself”(2 Ti 2:13).