I have a question regarding Mat 5:33-36 where Jesus forbids us to take oaths of any kind. Would this include pledges of allegiance to our nation, especially for immigrant Christians who would like to become American citizens?
I believe you may be putting words into the mouth of the Jesus. He did not say that we should not take oaths OF ANY KIND. That is not what he said. He is talking about oaths of a particular kind. We need to look at the context of the passage to find the heart, and therefore the application, of what Jesus is saying in Matthew. In the context, Jesus is talking about the Jew’s tendency to say something like this: “I promise! I swear by the temple.” Basically, Jesus is telling us that if we say we will do it, we should do it. Adding oaths should do nothing to increase the believability of what we say. We should “let our ‘Yes’ be ‘Yes’ and our ‘No’ be ‘No’.”
Therefore, if we promise to, for example, support the government of our nation or to uphold its constitution, if we are a Christian, it is not necessary to make an oath. We should simply keep our word. We should let our word be our bond, as they say. It is not necessary for us to take an oath and if we were giving that oath as some sort of extra boost to our integrity, then it would be sinful.
However, if we are asked to make an oath—if we are required by law or if we are required for our job—then it is not sinful to obey those we are submitting to and to take this oath. The context here is different from that implied in Matthew 5:33-36. For us as Christians, it is sufficient to simply say that we will do a thing for us to sincerely seek to do this thing with integrity. However, it is not a sin for us to give an oath required by someone we are submitting to if we are asked to make such an oath. It is not a sin because the issue of using a promise to prove to ourselves or others that we will actually do what we said is not present in this case. It is a matter of submitting to a governing authority, not of using a pledge to convince someone we are serious.
This may sound like a subtle distinction, but I believe that distinction is actually profound. It is a matter of Christian character that what we say we will do, we will do. Oaths are not needed and, in some cases, they are downright sinful. However, to make a required oath for a governing agency is not sinful in my opinion.