אור החיים — ועשו ארון עצי שטים

Q — Throughout the Mishkan the command is given in the singular — 'ועשית' (you shall make) — for every vessel, yet for the Aron it switches to the plural, 'ועשו ארון' (they shall make). Why this conspicuous change?

A — Or HaChaim addresses the midrashic puzzle (Shemot Rabbah 34) of why the Ark uniquely is commanded in the plural. The plural signals that the Aron — which houses the Torah — belongs to all of Israel collectively; every individual must have a share in it. Unlike the other keilim, the obligation and merit of the Ark that holds the Torah is not delegable to a single craftsman but pertains to the entire nation, so that all Israel shares in the crown of Torah it represents.