ועשו ארון עצי שטים ( תרומה כה:י)

And make the Aron (ark) from acacia wood

By all the other כלים (vessels) from the Mishkan; it says “ועשית” – you should make, and by the Aron it says “ועשו” and they should make it (plural form).  Because the Aron alludes to the כתר תורה – and the Torah is within reach to everyone, that’s why it’s in plural form.  Whereas the other vessels, the Shulchan and the Mizbeach, allude to the כתר כהונה & כתר מלכות, in which only the children of Aharon HaKohen and David Hamelech were worthy of using them. That’s why it’s “ועשו ” in the singular form when discussing those vessels.

Go back to Parshas Terumah