The reward promised to those who persevere is four-fold.
First, in v. 4, they will walk with Jesus in white. Some see a reference here to the resurrection body, but this is more likely a promise of victory and purity in the messianic kingdom when those who have remained faithful will experience the consummation of fellowship with Jesus. The reference to “white” may allude to the righteousness imputed to us in the act of justification. That is why they are regarded as “worthy”.
Second, the overcomer will be “clothed in white garments” (v. 5a; cf. 3:18; 6:11; 7:9-14;; 19:13).
Third, the overcomer will not have his/her name erased from the book of life.
There are at least five possibilities for this “book”.
(1) Hemer refers to one particular custom in Athens according to which the names of condemned criminals were erased from civic registers before their execution. The Greek word translated “to erase,” exaleiphein, “was the technical term for such degradation” (148). However, it is more likely that we should look for a biblical background to this imagery.
(2) In the OT the “book of life” (or its equivalents) was a register of the citizens of the theocratic community of Israel. To have one’s name written in the book of life implied the privilege of participation in the temporal blessings of the theocracy, while to be erased or blotted out of this book meant exclusion from those blessings. In other words, this book had reference to the rights of citizenship for the Jewish people (cf. Ex. 32:32; Ps. 69:28; Isa. 4:3).
(3) The concept of a “book” was also used to portray God’s all-inclusive decree (Ps. 139:16); i.e., the very days of one’s life are ordained and written in God’s “book” before one of them occurs.
(4) There is also the notion of “books” of judgment in which are recorded men’s deeds. They serve as that by which or from which one shall be judged (Dan. 7:10; Rev. 20:12).
(5) The most vivid usage, however, is the concept of the book as the register of those who have been chosen for salvation from eternity past. It is not temporal or earthly blessings that are in view, but participation in the eternal kingdom of God as recipients of eternal life (see Luke 10:20; Phil. 4:3; Heb. 12:23; Rev. 13:8; 17:8). It would appear from these texts that not all are written in this book, but only the elect. If it is the latter which Jesus has in view, there are three possible interpretations.
First, he may be saying that it is possible for a sinning, unrepentant Christian (such as were many at Sardis) to fail to overcome and thereby to forfeit their place in the book of life. Their names will be erased from that book and they will lose their salvation.
Second, others suggest that to have one’s name blotted out refers to something other than salvation. In Rev. 3:1 Jesus referred to the people at Sardis as having a “name” for being alive, i.e., they had a reputation for spiritual vitality. The idea, then, is that such people are saved, but will forfeit any hope of an honorable position in the coming kingdom of God. They are saved, but will experience shame at the last day. It is not the loss of life, per se, but the loss of a certain quality of life that otherwise could have been theirs. Thus, what one loses by having their name erased from the book of life is eternal rewards in the kingdom.
Third, others insist that the key is in identifying the “overcomers”. Those who overcome, it is argued, are Christians, indeed, all Christians. See 1 John 5:4-5; Rev. 21:7. This isn’t to suggest that Christians can’t backslide and sin badly. The rebukes in these seven letters indicate otherwise. Nevertheless, the evidence of the reality of true saving faith is perseverance (i.e., “overcoming”; cf. 1 John 2:19).
Three factors lead me to conclude that John does not envision the possibility of a true Christian forfeiting salvation. First, all of the other promises to the “overcomer” are coined in positive terms with no threat (implied or explicit) of losing a salvation once gained (see 2:7,11,17,26-27; 3:12,21). Second, if it is asked why this promise is couched in negative terms, the answer is obvious: Jesus couldn’t say “I will write his name in the book of life” because the names of the “overcomers” (i.e., the elect) were already written in the book from eternity past. Read Rev. 13:8; 17:8. There is no indication in Scripture, least of all in Revelation, of additional names being inscribed in the book as a reward for faithfulness or perseverance. Rather, faithfulness and perseverance are the evidence or fruit of having had one’s name written in the book. Those who worship the “beast” do so precisely because their names were not written in the book in eternity past (13:8; 17:8). Third, this declaration of Jesus is a promise to the elect that nothing will by any means (he uses a double negative) prevent them from possessing the eternal inheritance to which they have been ordained. In other words, we must take note of what Jesus does not say. He does not say that anyone will be erased from the book of life. Rather, he says the overcomers will notbe erased. His word is a promise of security to overcomers, not a threat of insecurity to those who lapse. So again, Jesus nowhere says he will erase names previously in the book of life.