1 Corinthians 5:1

It is everywhere reported that there is fornication among you, and such fornication as is not even among the gentiles, that one should have his fathers wife.

James 1:6-8

But let him ask in faith, nothing doubting; for he that doubteth is like a wave of the sea driven by the wind and tossed.

2 Peter 2:14

having eyes full of an adulteress, and that cannot cease from sin, alluring unstable souls, having a heart exercised in covetousness, children of a curse,

2 Peter 3:16

as also in all his letters, speaking in them of these things; in which things are some that are hard to be understood, which they that are unlearned and unstable wrest, as also the other Scriptures, to their own destruction.

Treasury of Scripture Knowledge

Summary

Unstable as water, thou shalt not excel; because thou wentest up to thy father's bed; then defiledst thou it: he went up to my couch.

Bible References

Unstable

James 1:6
But let him ask in faith, nothing doubting; for he that doubteth is like a wave of the sea driven by the wind and tossed.
2 Peter 2:14
having eyes full of an adulteress, and that cannot cease from sin, alluring unstable souls, having a heart exercised in covetousness, children of a curse,
2 Peter 3:16
as also in all his letters, speaking in them of these things; in which things are some that are hard to be understood, which they that are unlearned and unstable wrest, as also the other Scriptures, to their own destruction.

Because

1 Corinthians 5:1
It is everywhere reported that there is fornication among you, and such fornication as is not even among the gentiles, that one should have his fathers wife.