1 Peter 2:8

‘And, “A stone of stumbling, and a rock to fall over,” for they stumble at the word, being disobedient, to which also they were appointed.'

But to disbelievers, rather than being the chief cornerstone, Jesus has become a something that gets in the way, a stumblingstone, and an inconvenience. As they wander round the building site they trip over the very stone which should be the foundation of their lives. The citation is taken from Isaiah 8:14. The point is that He does not fit into their conceptions, and yet that He is unavoidable. And so they stumble at God's word by being disobedient. They turn from Him and refuse to enter into His obedience. They are ‘disobedient ones'. And significantly they do this because that is their destiny. It is the destiny to which they have been appointed (Romans 9:22). This may mean destined to stumble because they were disobedient, or even destined to disobedience (compare Romans 9:22).

Note the reference to being disobedient ones. Just as believers have been foreknown and sanctified in the Spirit into the obedience of Jesus Christ, so these people have been appointed to disobedience, or to stumbling because of they are ‘disobedient ones'.