Think of the high priest under the law. What he wore was very important. He was directed to wear "linen breeches" so that when he ascended the slope leading to the altar his naked thighs would not show. "And thou shalt make them linen breeches to cover their nakedness; from the loins even unto the thighs they shall reach" (Exodus 28:42).
God is interested in what our people wear--He says that this is the case! In speaking of assembly attire, the Spirit says, "In like manner also, that women adorn themselves in modest apparel, with shamefacedness and sobriety; not with braided hair, or gold, or pearls, or costly array; but (which becometh women professing godliness) with good works" (1 Tim. 2:9-10). The subject of the second chapter of first Timothy is the public assembly. The objective of this text is not to outline the precise clothing that is to be worn, but the manner in which we are clothed. "Modest apparel" is clothing that does not draw undue attention to the individual; clothing that is appropriate to wear in the presence of the Lord. The Spirit does not allow us the luxury of forgetting God when we dress.
My purpose is not to outline what is or is not proper attire. It is imperative, however, that the people themselves give thought to this matter. Our gatherings are certainly not to degenerate into a showcase for the latest clothing styles. Neither are we to suppose that God is unconcerned about our appearance. We are coming before God, let us conduct ourselves appropriately. If God did not want to see the "nakedness" of the high priest, you can rest assured He does not want to see ours either. After all, He has not changed, even if people have.
A personal note is in order at this point. Having raised ten children, I have given considerable thought to the development of a godly conscience in them. We have consistently taught our children that God is deserving of only the best. You never give your second best to the Lord. You give Him the best of your person and resources. Casualness before Him is always out of order. All of your resources should be marshaled and kept in control when you stand before God. My suggestion is that informality does not contribute to this process. We have taught our children to apply this to the clothing that they wear to the assembly, and to the offerings they give, as well as their mental alertness. Saturday night is not the time to stay up late indulging in pleasures and other interests unrelated to our salvation. We should not be offering lame lambs of thought and appearance to our Savior.
Having said all of this, dictating the manner of dress for the assembly is not in harmony with the new covenant. Change for the good, or spiritual improvement, must always be the result of growth in Christ. To put it another way, people must have a reason to change. An awareness of the purpose for gathering, with a sense of the presence of the Lord and a desire to please Him, will provide a basis for each member to do their best for the Lord--even in dress.