It is worth noting that there a similar questions on this website, and numerous articles that cover this topic, however most of these seem to address the question from a standpoint of refuting Bible skeptics and give rather short answers, dismissing it as a non-issue for the authenticity of Jesus' resurrection. I agree with their conclusion, however their arguments don't seem to do justice to the textual evidence that the disciples (and others close to Jesus) did not recognize him.
The reason I am interested in this is because I am interning at a youth group going through the book of John. The first evidence in the book of John that someone who knew Jesus well did not recognize him after his resurrection is Mary in Jn. 20:14-18. At least once more in this chapter, and then again in chapter one it is mentioned that someone (or a group of people) do not recognize Jesus immediately. At first it did not seem that this idea of those close to Jesus not recognizing him was significant to the meaning of the text, however, due to the repetition, I am questioning whether it may be more important than I thought.
First, it is worth noting that there are a number of passages that mention that people did not recognize Jesus do have simple and reasonable explanations. The three main places where it is mentioned are in John 20:14, John 21:4, and Luke 24:15-16. In the first passage, John 20:14, Jesus appears to Mary near the tomb and she does not recognize him at first, until he says her name. The argument goes that Mary did not recognize him because she was weeping, it was early in the morning, and Jesus may have been far away (see 20:1, 15-16). In John 21:4 Jesus meets seven of the disciples while they are fishing and calls to them from the shore. The text mentions that the disciples were about 100 yards from the shore (verse 8) and, again it was early in the morning (verse 4). It is argued that at a distance of 100 yards with bad lighting, the disciples would not have recognized Jesus. In the third passage, Luke 24:15-16, Luke specifically mentions that "their eyes were kept from recognizing him."
These are the three texts that specifically mention that people close to Jesus did not recognize him after his resurrection. However, with the exception of the passage in Luke, the other two explanations do not seem convincing, especially when considered alongside Jesus appearing to his disciples in the second half of John chapter 20 where it is implied at least once, if not twice, that the disciples did not recognize Jesus. Those instances are discussed below. As to the two explanations for passages in John, the explanation of Mary not recognizing Jesus is not convincing because in the passage it says that Mary first goes to the team while it was still dark, but then runs to tell Peter and John (verse 1) and then apparently returns (either walking or running, presumably behind Peter and John) and at least some time has passed. It very well may have been light at this point. Furthermore, it seems doubtful that it was still dark since Peter looks into the tomb and sees the head cloth folded up in a place by itself. This would be difficult to do if the sun had not yet risen (although admittedly not impossible). If it was light out, Mary should have been able to recognize someone she knew as well as she knew Jesus, even if he was not standing next to her but many yards away. The explanation of John 21 is even less convincing. I can recognize anyone I know well at a distance of 100 yards, even without perfect lighting. Even if Jesus did look significantly different after his resurrection the disciples at this point had already seen him on two different occasions in John chapter 20.
On its own, this does not seem like any reason to raise questions as to why Jesus was unrecognizable, the reasons for why Jesus was not recognized at first seem reasonable, but when paired with the record of Jesus' appearances to the disciples behind locked doors in John 20, these explanations seem less reasonable. In John 20, Jesus appears to Mary, and then to the disciples while they are behind locked doors (Luke's gospel records that in between these events Jesus talks with the two men on the road to Emmaus, this will be considered below). When Jesus appears to them, he says "peace be with you," and then he shows them his hands and his sides (John 20:20-21). John then says "then the disciples were glad when they saw the Lord." This seems to indicate that they did not recognize him until they saw the holes in his hands and his side. Why was he unrecognizable before this?
The parallel passage in Luke comes to bear on this as well. Luke records that on the road to Emmaus two of Jesus disciples (or followers, one of whom was cleopas) do not recognize him (see Luke 24:13-16, 18). As mentioned before, Luke specifically records that "their eyes were kept from recognizing him." This, on its own, seems to raise the question of whether Jesus looked different after his resurrection. John 20 tells us that he still had the wounds, but the disciples on the road to Emmaus don't recognize him, which seems to indicate he does not look the same as he does in the passage in John, and in the passage immediately following the story of the road to Emmaus.
After they make it to Emmaus, Jesus shares a meal with him, and "their eyes were opened, and they recognized him. And he vanished from their sight" (Luke 24:31). John then records that they return to Jerusalem and tell "the eleven and those who were gathered with them" what had happened (verse 35). Furthermore, Luke records that the Lord had appeared to Peter (verse 34). Luke then records Jesus appearing to the group of them in the room with the locked doors and showing them his wounds (parallel to John 20). Luke says in verse 37 "But they were startled and frightened and thought they saw a spirit." It does not seem that they recognized Jesus either. In this room were at least four people who had recognized Jesus post resurrection, Mary, Cleopas, the other disciple on the road to Emmaus, and Peter. While it could be true that these four recognized Jesus, Luke simply records that the group as a whole was "startled and frightened," an unlikely response for people who recognize their Lord!
The question remains. Why did those who knew Jesus not recognize him? It seems that something must have been different about him. Mark 16:12 records that Jesus "appeared in another form to two of them, as they were walking into the country." This is a possible explanation, that Jesus changed forms, however, the last twelve verses of Mark are suspect, and may or may not have originally been part of the book of Mark. That being said, many scholars who believe that these verses were not originally included still believe that they record things that actually happened. This could possibly be a good explanation of why those closest to Jesus did not recognize him.
Is anyone aware of any other possible explanations? Are there any scripture passages that come to bear on this?
Edit: I forgot to mention that in John 21, John goes out of his way to say in verse 12, "Now none of the disciples dared asked him, "Who are you?" They knew it was the Lord." This should be obvious, that they recognize the man they spent three years with, but John takes the time to mention it. It seems Jesus looked different from before he was crucified and rose, and possible even different from the first two times he appeared to them after his resurrection on John 20.