It's an interesting verse. "Worship the Lord in holy attire," is, of course, the New American Bible translation. The Vulgate is, "Adorate Dominum in decore sancto," which Douay Rheims renders, "Adore the Lord in holy becomingness." Other translations have "holy array," "the splendor of holiness," "the beauty of holiness," and even "reverent grace."
"Holy attire" is good for making the point that how we dress for Mass matters. That expression could be rendered informally as "church clothes," since to be holy is to be dedicated to God. The idea that what we wear to Mass should be something set aside, not to be used for non-religious purposes, is ... well, okay, it's extreme, except for priests, deacons, and altar servers. But the idea that our participation at Mass is a liturgical act, and that therefore how we dress for Mass is also a liturgical matter, isn't so much extreme as unthought.
What I like about the Douay Rheims's "holy becomingness" is that it encompasses attire but extends much further. We speak of a becoming modesty, a becoming honesty, a becoming gratitude -- in short, becomingness encompasses both physical appearance and the appearance of virtue.
We should worship the Lord, then, not only in our good clothes, but in our good habits. (Of course, for somepeople, their clothes are habits, but you see what I mean.)