The key must be sought in the exilic and post-exilic age where, unfortunately, direct and decisive evidence is lacking.
Collections of laws are found in Deuteronomy and in exilic and post-exilic writings; groups of a relatively earlier type are preserved in Exod.
This is especially true of the history of the exilic and post-exilic periods, where the effort is made to preserve the continuity of Israel and the Israelite community (Chronicles - Ezra - Nehemiah).
Although these and other phenomena cannot yet be safely placed in a historical frame, the methodical labours of past scholars have shed much light upon the obscurities of the exilic and post-exilic ages, and one must await the more comprehensive study of the two or three centuries which are of the first importance for biblical history and theology.
The embodiment of political and religious supremacy displayed in the high priest's authority, clothing and symbols can only reflect exilic or rather post-exilic conditions.'