Adams on Psalm 69:28

28 Let them be blotted out of the book of the living, etc We come to the question, Whether to be written in heaven be an infallible assurance of salvation; or, whether any there registered may come to be blotted out? The truth is, that none written in heaven can ever be lost; yet they object against it this verse. Hence, they infer, that some names once there recorded are afterwards put out; but this opinion casteth a double aspersion on God himself. Either it makes him ignorant of future things, as if he foresaw not the end of elect and reprobate, and so were deceived in decreeing some to be saved that shall not be saved; or, that his decree is mutable, in excluding those upon their sins whom he hath formerly chosen. From both these weaknesses St Paul vindicates him (2 Tim 2:19): "The foundation of God standeth sure, having this seal, the Lord knoweth them that are his." First, "The Lord knows them that are his; "this were not true if God's prescience could be deluded. Then, his "foundation stands sure;" but that were no sure foundation, if those he hath decreed to be his should afterwards fall out not to be his. The very conclusion of truth is this impossibilis est deletio; they which are "written in heaven" can never come into hell. To clear this from the opposed doubt, among many, I will cull out three proper distinctions:
1. One may be said to be written in heaven simpliciter, and secundum quid. He that is simply written there, in quantum praedestinatus ad vitam, because elected to life, can never be blotted out. He that is written after a sort may, for he is written non secundum Dei praescientiam, sed secundum praesentem justitiam - not according to God's former decree, but according to his present righteousness. So they are said to be blotted out, not in respect of God's knowledge, for he knows they never were written there; but according to their present condition, apostatising from grace to sin. (Nicholas of Lyra)
2. Some are blotted out non secundum rei veritatem, sed hominum opinionem - not according to the truth of the thing but according to men's opinion. It is usual in the Scriptures to say a thing is done quando innotescat fieri, when it is declared to be done. Hypocrites have a simulation of outward sanctity, so that men in charity judge them to be written in heaven. But when those glistening stars appear to be only ignes fatui, foolish meteors, and fall from the firmament of the church, then we say they are blotted out. The written ex existentia, by a perfect being, are never lost; but ex apparentia, by a dissembled appearance, may. Some God so writes, in se ut simpliciter habituri vitam - that they have life simply in themselves, though not of themselves. Others he so writes, ut habeant non in se, sed in sua causa; from which falling they are said to be obliterated. (Thomas Aquinas)
3. Augustine says, we must not so take it, that God first writes and then dasheth out. For if a Pilate could say, Quod scripsi, scripsi - "What I have written, I have written," and it shall stand; shall God say, Quod scripsi expungam - What I have written, I will wipe out, and it shall not stand? They are written, then, secundum spem ipsorum, qui ibi se scriptos putabant - according to their own hope that presumed their names there; and are blotted out quando ipsis constet illos non ibi fuisse - when it is manifest to themselves that their names never had any such honour of inscription. This even that Psalm strengthens whence they fetch their opposition: Let them be blotted out of the book of the living, and not be written with the righteous. So that to be blotted out of that book, it is, indeed, never to be written there. To be wiped out in the end, is but a declaration that such were not written in the beginning.

As quoted in Spurgeon's Treasury of David.