i know i've written about this before, but it's on my mind again. i don't think dressing up for worship gatherings should be taught as a binding custom (and more strongly, i think it ought not be practiced whether bound by someone else or not) because:
1. It equates wealth or materialism with reverence. The niceness or professional-like-aesthetic of one's clothing is seen as showing respect and reverence toward God. This custom thus equates a material end with a spiritual end.
Consider an analogous case with singing: Does it seem spiritual or Christ-like or right to say that because someone doesn't have a singing voice which meets a certain cultural aesthetic standard, that person doesn't have the level of devotion or heart-felt-ness in their praise in comparison to someone who does have an aesthetically pleasing singing voice? Would we say that a "better" singer is in some sense more spiritual than a "worse" singer? What if a person could spend the time to train his voice to become a better singer, but refused to do so? Should we say that such a person is somehow spiritually defficient because he could improve his musical skills but won't? My intuition says that by and large no one would find such a person blameworthy. If that is the case, then, similarly, why should people feel they are less spiritual for not being "better" dressers?
2. It is conducive to character judgments based on appearance. First, if reverence is equated with a certain spectrum of appearances, then those who choose to fall into that range of appearance will assume by their own appearance that they are therefore reverent. However, even the most sharply dressed person is not necessarily reverent. And more to the point, if a person is irreverent, no level of professional-like apparel with alter or improve that irreverence. Yet people holding to this notion of nice-apparel indicating reverence are more likely to believe they possess the attitude or disposition of reverence due to their appearance.
Second, if reverence is equated with a certain spectrum of appearances, then those within that spectrum of appearances are likely to mark those who fall outside that range of appearance as irreverent. This notion, if i believe it, urges me toward assuming things about others' relationship with God based solely on their clothing. Is this qualitatively any different than the Pharisees assuming that Jesus couldn't possibly have been the Christ because He socialized with less-than-reputable classes of people or didn't make His disciples ceremonially wash their hands?
3. It is conducive to partiality. Believing this notion creates a division between those who fall within that range of appearances deemed as "reverent" and those who fall outside it. Thus, it is conducive to people preferring to keep company with "their own kind." People who believe that falling within that range of appearances correlates with a higher level of some spiritual quality are likely to be more comfortable and open to others who also fall within that same range of appearances.
James says quite explicity that no preference or partiality should be shown based on niceness of clothing (James 2:1ff). Many people have explained his words by adding this qualification to the dressing-up-rule: People just need to be doing the best they can do; as long as they're wearing they're personal best, they're fine. However, this passage in James mentions no such qualification. There's nothing in this passage that indicates James shares this underlying qualification in the matter. Rather, James states in a raw way that partiality based on niceness of clothing are forbidden.
Further, however noble this qualification sounds ("as long as someone wears his personal best..."), it doesn't change the fact that there is a majority demographic of a certain appearance level. If i do not fall within that majority demographic, then no matter how many times people within that demographic tell me i'm okay based on this qualification, there is nevertheless a clear and obvious difference between me and those within that demographic--i don't belong to this group. Imagine if you were to wear your suit into an assembly and when you walked in, every one else in the room was wearing tattered and worn rags reminiscent of homeless people. Would you not be uncomfortably aware of the difference between you and them? If some of them discreetly tried to comfort you by saying since you're wearing your personal best, it's fine that you don't look like the rest of them--would that make you any less aware in a social sense of the difference between you and them?
The point being that this particular practiced even when framed in a nicer way is still conducive to an air of exclusion and preference--exclusion and preference based on criteria over which no one ought to be excluded or preferred.
4. It is conducive to hypocrisy. If people equate certain appearances with certain character states, then they are likely by appearance and to others who believe this notion to present themselves as having certain character states that they do not, in fact, have. In other words, lending such weight to appearances leads to pretenses and "masks." When i dress up to call attention to some spiritual disposition i'm supposed to have at a certain time and place, you are seeing how i appear to be but not necessarily who i really am.
Further, if i dress this way only on a certain occasion, and if there are those who basically only see me on that certain occasion, then in a practical way, others are disallowed access to who i am normally outside that occasion.
i think integrity can be described as being the same person in character and virtue at all times. To have integrity is not to be, as it were, two-faced--a different person in character on one occasion than on another. Yet it seems that this custom of dressing up for church is conducive to that very thing.
5. It creates a perceived, yet erroneous, difference between the "sacred" and the "secular." i am personally unable to discern from the New Testament that Christians assembling together is a "special occasion" or "sacred" in the sense that it is often treated in modern times. Is it really the case that i'm somehow more obligated to revere God during an assembly than any other time? Is it the case that i'm somehow more in the presence of God when i assemble with other Christians to pray compared to when i pray privately on some other occasion? When i assemble with other Christians and participate in that assembly, am i somehow moreso serving God during that time than i am when i live the way God wants me to live during any other given time in my life? To put it candidly, does God care that i look nice during church but He doesn't care if i look nice at work?
i think dressing up for church buttresses the notion that there is a difference between Sunday and every other day of the week in regards to my discipleship. Am i any less obligated to follow Christ any other day of the week? Am i any less obligated to revere God any other day of the week? Am i any less obligated to "be on my best behavior" any other day of the week? If none of these obligations change at any given time, and if a certain appearance is indicative of meeting those obligations, why would any Christian be any less obligated to dress up any other day of the week?
i think it is a false and unbiblical notion to say that parts of my life are less "spiritual" or less "sacred" or less important to God than others. Of course, i should sing and pray to the glory of God when assembled with other Christians. But nonetheless should i pursue my career to the glory of God or vacation to the glory of God or play with my son to the glory of God. i am no less a Christian outside an assembly of Christians than when i am in one. If there is something distinctively Christian about dressing up, then why wouldn't i be obligated to dress up at all times?
6. There's no New Testament precedent for it. Why do we take the Lord's Supper? Why do we pray together? Why do we assemble regularly? Why do we send and support missionaries? Why do we study the scriptures? We find these things practiced by and enjoined upon the New Testament church and we believe we ought to imitate them. Dressing up for church is clearly a wide-spread custom in our culture such that some (maybe even many) consider it obligatory. But where is the New Testament precedent for it? Where does the New Testament show us that this practice was customary and sanctioned by the New Testament church? Unless i have completely missed some scriptures somewhere, it seems this custom is one of human invention and initiative rather than from God.