The Coat, the Turban and the Girdle.
“And you shall weave the under-robe in patterned work of fine linen, and you shall make a turban of fine linen, and you shall make a girdle, the work of the embroiderer.”
The under-robe is pure white, delicately woven and patterned. The turban too is white. Both are of fine linen. The under-girdle is to be embroidered, and is to be of fine linen, blue-violet, red-purple and scarlet (Exodus 39:29). The white is a picture of purity and righteousness covering the whole person, a righteousness possible because the appropriate sacrifices have been made from an honest heart. But the weaving and the patterning and the embroidery suggest an added something to the white indicating that God has added to them something of His own purity and holiness. But these clothes are on the whole hidden, so why the delicate work? The answer is that in all things to do with God man must take the greatest care and trouble. All must be done to the glory of God, even that which is not seen.
Summary. So prior to coming forward to fulfil his priestly duties Aaron must robe himself in a pure white under-robe which covers his person, with its multicoloured girdle patterned on the curtains of the Sanctuary, and put on his pure white turban. Then he puts on his robe or tunic of blue-purple, over which he dons the multicoloured ephod together with the attached breastpouch, and finally he dons the golden plate which declares Him and Israel as ‘holy to Yahweh'.
He is thus a picture of Christ Who will come pure in righteousness, girdled by God in His strength and holiness, bearing in Himself His people whose representative He will be, bearing also all that is necessary for judgment and marked off uniquely as ‘holy to Yahweh'.