Are you asking for when saved believers stop abiding in Him?
John 15:6 If a man abide not in me, he is cast forth as a branch, and is withered; and men gather them, and cast them into the fire, and they are burned. 7 If ye abide in me, and my words abide in you, ye shall ask what ye will, and it shall be done unto you.
Or are you asking for proof that believers that stop abiding in Him are still saved?
2 Timothy 2:18 Who concerning the truth have erred, saying that the resurrection is past already; and overthrow the faith of some.
Paul just gave an example of a former believer above, yet he points out next how that foundation and that seal is sure for why een former belevers and not just those who have gone astray, are to be called to depart from iniquity.
19 Nevertheless the foundation of God standeth sure, having this seal, The Lord knoweth them that are his. And, let every one that nameth the name of Christ depart from iniquity.
Now look at what is in His House. There are 2 kinds of vessels that are in His House.
20 But in a great house there are not only vessels of gold and of silver, but also of wood and of earth; and some to honour, and some to dishonour.
Now look at how departing from iniquity makes one a vessel unto honor in His House below.
21 If a man therefore purge himself from these, he shall be a vessel unto honour, sanctified, and meet for the master's use, and prepared unto every good work.
So those who do not depart from iniquity are what? The vessels unto dishonor in His House, the vessels of wood & earth, but still saved because they are in His House.
That is what the OP is about; OSAS but be ready or else.