John Wesley on Numbers 4:12

The instruments of ministry - The sacred garments used by the priests in their holy ministrations. Cover them - All these coverings were designed, For safety, that these holy things might not be filled by rain, or tarnished by the sun. For decency, most of them had a cloth of blue, or purple, or scarlet over them; the ark, a cloth wholly of blue, perhaps an emblem of the azure skies, which are spread between us and the Majesty on high; For concealment. It was a fit sign of the darkness of that dispensation. The holy things were then covered. But Christ hath now destroyed the face of the covering.