1 – In Luke 24 we read that two disciples met Jesus and talked with him but did not know him! We read also about Mary Magdalene who did not know Jesus at first in John 20. Jesus appeared again in John 21 to the disciples but they did not recognize him!!! Doesn’t this support the theory that they did not see Jesus but saw another man? 2- Does Matthew 5 : 37 mean that we can’t say for example ” I swear that Jesus is the Son of God”? or ” I swear that God loves us”?
The most reasonable explanation of Luke 24:16, John 20:14 is that these people believed Jesus to be dead and had no expectation for him to rise from the dead. If we are completely convinced that someone is dead, then our minds will resist telling us that we saw that person. Besides, in Luke 24:16 we are told that God prevented them from recognizing him. This may be a factor in what happened. The situation in John 21:7 is different, because in this case, the apostles already knew that Jesus had raised from the dead. In this case, they were at a distance, fishing and probably did not recognize Jesus simply because they were far away. It is not that they did not recognize him, but simply that they could not see the person on the shore clearly until they came closer or looked more carefully.
The Muslim contention here is that these people were simply mistaken and they did not in fact see Jesus resurrected. The problem with this explanation is that it requires that once they thought they recognized Jesus they were simply wrong. Which is more likely, 1. that one not recognize someone but later recognize them or 2. that one would think they did not recognize another but then changed their mind and recognized them, when it was simply another person? Think about your own experience. Has anything like the scenario the Muslims proposed–the second one above–ever happened to you or to anyone you know? Once you recognize a person, you will begin to talk to them and if your identification were incorrect, you would realize it right away. You say to someone, “Oh, hi Mario.” If it were not Mario, then the person would say, sorry, you are mistaken. This would especially be the case with Jesus. Imagine someone saying incorrectly, “Oh, you are Jesus.” and the person not correcting them under the circumstances. This is not a rational explanation of the events. On the other hand, all of us have had occasions where we met someone whose visage had changed somewhat for some reason and we did not at first recognize that person, only to later realize who it was for some reason. This is simply a matter of Muslims looking for an interpretation which opposes the Christian view, without even thinking about whether their alternative explanation makes sense. They do not do what they should do, which is ask what is the most reasonable explanation. They are simply looking for excuses to dismiss the obvious conclusion so that they can find an excuse to criticize Christianity.
Besides, there is the embarrassment factor. Why would the Christian writers include such stories if they were not true? Their object is that we believe that Jesus raised from the dead. If they were trying to deceive people about that (what the Muslims are trying to claim), why would they include a story in the gospels which is embarrassing such as this one? The only reasonable conclusion is that these stories are there because this is what happened.
Let us add this fact. There were many appearances of Jesus after he was resurrected from the dead in which multiple people recognized Jesus. In John 20:19-23 he appeared to all the apostles except Thomas, talking to them, showing them the wounds in his hands and side. It would be ludicrous to propose that they were all simultaneously mistaken in this case that this was in fact Jesus. It is quite impossible for this entire group to be deceived about who Jesus was. So, even if we can accept the Muslim thesis that in Luke 24:16 and John 20:14 their identification was mistaken (an extremely unlikely conclusion), what would this prove? Would it prove that the several other appearances before larger groups, all of whom believed it was their closest friend in the world were mistaken? Obviously not. So, what is the Muslim trying to prove here? I believe they are just trying to sow confusion in believers. We should ignore these self-serving and insincere attempts to undermine the Christian gospel.
On your second question, I believe that Matthew 5:37 can be interpreted to tell us that we should not swear to things. We should simply let our word be our word. If we are always honest, then swearing to something would add nothing to the veracity of what we say. With a Christian, who would never lie, why would they need to tell someone that they were not lying by swearing to a thing? This makes no sense. So I say yes, this is how we should interpret this passage. We should not swear that God loves us or that Jesus is the Son of God. We should simply declare these things to be true and let people decide for themselves. Besides, one can argue that to say that God loves us or that Jesus is the Son of God is an opinion. Why would one swear to an opinion? It makes no sense. We would never say “I swear that apples taste better than oranges.” Instead we would say, “I think apples taste better than oranges” or something like that. We only swear as to matters of fact. Now, I am an American and there may be a culture in which people swear to things that are a matter of opinion. Even if this were true, I say that, based on Matthew 5:37 a Christian should not swear, even to an opinion.