Psalms 69:28 - Coke's Commentary on the Holy Bible

Let them be blotted out of the book— This means no more than that they should be cut off, and die before the usual time. We have before observed, that God is sometimes represented as recording and entering in a book the conception, birth, sufferings, actions, and punishments of his people: so here, and in other places, he is represented as keeping a list or roll in which the names of all his people are entered. The allusion seems to have been taken from the custom of generals and commanders of armies, who, upon the desertion or death of a soldier, strike him out of the muster-roll. This is what Ezekiel alludes to, Ezekiel 13:9 where he calls it, The writing of the house of Israel; and to be written or entered in that list, signified the same thing as being acknowledged for one of God's people. Compare Isaiah 4:3. As great immorality and apostacy, such as are the subjects of this psalm, may well be deemed a sort of spiritual desertion, the allusion is applied here with great propriety.