Verses with the word unstable in the New Testament (3 verses):

James 1:8
A double minded man is unstable in all his ways.

2 Peter 2:14
Having eyes full of adultery, and that cannot cease from sin; beguiling unstable souls: an heart they have exercised with covetous practices; cursed children:

2 Peter 3:16
As also in all his epistles, speaking in them of these things; in which are some things hard to be understood, which they that are unlearned and unstable wrest, as they do also the other scriptures, unto their own destruction.