Gospel Guidebook: Getting and Keeping It Right 
Does John 10:4-5 Teach that All Believers Endure to the End?
Initial Considerations
In John 10:1-5, we read the following: 1 Verily, verily, I say unto you, He that entereth not by the door into the sheepfold, but climbeth up some other way, the same is a thief and a robber. 2 But he that entereth in by the door is the shepherd of the sheep. 3 To him the porter openeth; and the sheep hear his voice: and he calleth his own sheep by name, and leadeth them out. 4 And when he putteth forth his own sheep, he goeth before them, and the sheep follow him: for they know his voice. 5 And a stranger will they not follow, but will flee from him: for they know not the voice of strangers.
It is sometimes said, particularly among those who hold a Reformed view of salvation, that John 10:4-5 teaches that all truly born-again believers will become disciples and endure in their faith until the end of their lives. In particular, they "follow the shepherd" and "flee from the stranger." Now, while I agree that believers usually become disciples and endure in their faith until the end of their lives, I disagree that believers always do these things. Discipleship and endurance are not conditions for receiving eternal life, nor do such things play a role in maintaining eternal life. Something eternal, by its very nature, does not need to be maintained in the sense that it could be lost. It is impossible for something eternal to become non-eternal. Jesus told us plainly in John 3:15 that everyone who believes in Him receives eternal life. Jesus explained what he meant by "believe" in John 3:11-12. In those verses, we see that "believing" equates to receiving testimony as being true. When we believe in Jesus by receiving His testimony as being true in John 3:15, we receive eternal life.
Regrettably, many people are not satisfied with simply receiving Jesus' testimony as being true. Many people insist that the word "believe" includes "other conditions," such as repentance of sins, and life-long commitment, discipleship, and endurance. Although proponents of these "other conditions" often don't like to admit it, they are creating a conditional salvation that depends on works. Some of these people call the works "evidence of true conversion," while others call them "God produced works" or "non-meritorious works of grace." They often use cleverly crafted labels like these to try to extricate themselves from the implications of these "other conditions." However, regardless of what label is used, these conditions become an essential element of salvation. From the perspective of Free Grace Theology, these conditions nullify the free grace of God in justification (Romans 3:24). They basically turn God's gift of salvation into a contract with various stipulations.
Before, getting into John 10:4-5, it is important to recognize that there are plenty of examples in the New Testament of born-again believers becoming deceived and "following a stranger." It happened with the Corinthians (2 Cor. 11:4), Galatians (Gal. 3:1), Ephesians (Acts 20:30), some among the seven churches in Asia (Revelation 2 and 3), and some of those of whom the Apostle Peter wrote (2 Peter 2:20-22, cf. 2 Peter 1:8-9). And there are even cases of full-blown apostasy in the New Testament. Some of the Hebrews apostatized (Hebrews 10:25-26), and yet, we are assured that they were still "sanctified once for all," "perfected forever" (10:29, cf. 10:10, 14), and "God's people" (10:30). The Apostle Paul wrote that even if we don't believe, Jesus would remain faithful (2 Timothy 2:13). In Jesus' explanation of the parable of the sower in Luke 8:11-15, He says that there are some saved believers who fall away and fail to bear fruit. Please see me article on Luke 8:12-13 for more details. At any rate, these examples should, at the very least, give interpreters of John 10:4-5 pause before concluding that the parable teaches life-long discipleship and endurance.
In addition to the above examples, the doctrine of life-long discipleship and endurance just doesn't seem consistent with the repeated warning passages that we find throughout the New Testament. For example, the letter to the Hebrews basically serves as an apologetic for the faith and a warning against apostasy. If true believers really can't fall away, large portions of the letter to the Hebrews merely become hypotheticals that have no real application. Since true believers supposedly can't fall away, the penalties stipulated in those warning have no application to them. On the other hand, false believers can't fall away either, since they were never truly saved to begin with. Therefore, the penalties stipulated in the warning passages have no real application to them either. Now, I grant that God may be using the warning passages to motivate believers to do what they have been predestined to do, without any real application of the penalties stipulated in those warnings. However, this line of thinking seems more adapted to fit one's theology than it does Scripture. It just seems more likely to me that those warning passages exist simply for the fact that the penalties stipulated by them have real application. In the case of the Hebrews, the author seems to be strongly implying in Chapter 10 that the penalties of apostasy will be applied to the believers mentioned in verses 25-26, despite them still being "God's people" (10:30).
Overall Considerations regarding John 10:1-5
John 10:1-5 is a parable, so we should really be careful not to read too much into the figurative language. People who view verses 4-5 as teaching life-long discipleship and endurance regard those verses as applying to the experiential sanctification of the believer. I don't think this interpretation should be accepted at face value, and I will shortly give my reasons for why I regard the parable as symbolizing positional justification. However, for the sake of argument, let's just assume for a moment that verses 4-5 do symbolize the experiential sanctification of believers. In this instance, we would still have to be careful not to read too much into it. Many people read verses 4-5 and conclude that what is true of the whole flock must be true of the individual. However, this is the logical fallacy of division. The "they" in verses 4-5 refers to the whole flock, not the individual sheep in the flock. In verse 3, the shepherd does call his sheep by name (implying treatment of the sheep on an individual basis), but notice that after he puts them out from the sheepfold, he goes before them. The sheep are behind him, and in someways left to themselves to follow the shepherd. This is where we have to be careful not to apply the fallacy of division. When we apply this interpretation to the body of believers, what may be characteristic of the whole body might not always be true of the individual member. Another example where this fallacy is often committed is in Ephesians 2:1-3. What is true of the Ephesian church as a whole, may not be true of all individuals in that church. In the case of the Ephesians, we know that at least some of them did get carried away with heresies (Acts 20:29-30) and they were criticized for leaving their first love (Revelation 2:4-5). Of course, these two instances might have happened years or decades apart from each other, but they still serve sufficiently to show that even good churches can have some bad individuals. As a result, even if verses 4-5 are referring to experiential sanctification, they cannot be used as a proof text to show that all believers are successful in life-long discipleship.
It is also important to note that John 10:1-5 is not a particularly easy parable to interpret. The Apostle John tells us this explicitly in verse 6: "This parable spake Jesus unto them: but they understood not what things they were which he spake unto them." It is never wise to build foundational doctrines from parables, apocalyptic language, and figurative language. There are plenty of plain statements in the Bible, and these plain statements should be used to interpret the obscure statements, not the other way around. Sadly, however, countless numbers of people have built foundational doctrines from the parables of Jesus in the four gospels and from the apocalyptic and figurative language in Book of Revelation. In the case of John 10:1-5, Jesus partially explains it and partially expands on it in verses 7-18 and 24-29. I will be referring to those verses to support my explanation.
As a final comment before explaining why I think John 10:1-5 refers to positional justification, it is important to note that the Gospel of John is full of metaphors for "believing." "Believing" is referred to in the context of "receiving" (1:11-12, cf. 1:7), "drinking" (4:14, cf. 6:35, 7:38), "eating" (6:35, cf. 6:29, 6:47-51), "coming" (6:37, 6:45, cf. 6:36, 6:40, 6:47), "following" (8:12, cf. 12:35-36, 12:46), and "seeing" (9:39, cf. 9:35-38). I believe that the expression "hearing and following" in John 10:4-5 is also a metaphor for "believing."
John 10:1-5 and Positional Justification
I believe that John 10:1-5 refers to the incarnation of Jesus and His calling of His people out of the world. Jesus is represented by the shepherd (10:11, 10:14). Satan and his servants are represented by the one who climbs up wall of the sheepfold as a thief and robber (10:8, 10:10, cf. 8:44). The world (or perhaps Israel, cf. 10:16) is represented by the sheepfold (10:27, cf. 15:18-19, 17:14). The people of the world (both believers and unbelievers) are represented by the sheep (10:7, 10:26). Believers are represented by Jesus' sheep (10:26-27, cf. called out of the world in 15:18-19, 17:14). Unbelievers are represented by the sheep who "belong to another" (which is the literal translation of "a stranger" in verse 5) (10:5, cf. 5:43, 8:41, 8:44). Believing is represented by "hearing and following the shepherd" (10:25-26). Refusing to believe another for salvation (i.e, receiving a false messiah) is represented by "not hearing and fleeing a stranger" (10:8, in contrast with 5:43). Eternal security (receiving eternal life, never perishing, and being secure in the hand of Jesus and the Father) is represented by protection from the stranger, thief, and robber (10:10-15, 10:28-29). The Father may be represented by the porter (10:3). The Holy Spirit may be represented by the door "into the the world" (10:1-2). Salvation is represented by the door (i.e., Jesus) "out of the world" (10:7, 10:9).
I believe that if we read John 10:1-5 with the above representations in mind, it is easy to see that the parable could symbolize Jesus coming into the world as Messiah by the Father and the Holy Spirit in order to call His people out of the world and save them. If this interpretation is correct, it would refer to positional justification. In verses 7-18 and 24-29, Jesus expands on the parable to include some aspects of experiential sanctification, such as "going in and out to find pasture" in verse 9 and experiencing "abundant life" in verse 10.
As I mentioned above, John 10:1-5 is not an easy parable to understand. There have been many and various interpretations of it throughout the years. My interpretation is not entirely novel. I got the basic concept for it from a paper called The Shepherd's Door꞉ An Incarnational Reading of John 10꞉1-5 by Douglas Estes.
I hope that this article serves to show that an experiential sanctification interpretation of John 10:4-5 should not be accepted at face value. Furthermore, even if that interpretation is accepted, it cannot be used as a proof text for showing that all believers persevere in discipleship until the end of their lives.