'The leathern girdle' which John the Baptist wore signifies an external band that receives and contains interior things.

(References: Arcana Coelestia 9372)

665. That to “set up a covenant” signifies that he would be regenerated, is very evident from the fact that there can be no covenant between the Lord and man other than conjunction by love and faith, and therefore a “covenant” signifies conjunction. For it is the heavenly marriage that is the veriest covenant; and the heavenly marriage, or conjunction, does not exist except with those who are being regenerated; so that in the widest sense regeneration itself is signified by a “covenant.” The Lord enters into a covenant with man when He regenerates him; and therefore among the ancients a covenant represented nothing else. Nothing can be gathered from the sense of the letter but that the covenant with Abraham, Isaac, and Jacob, and so many times with their descendants, was concerned with them personally, whereas they were such that they could not be regenerated; for they made worship consist in external things, and supposed the externals of worship to be holy, without internal things being adjoined to them. And therefore the covenants made with them were only representatives of regeneration. It was the same with their rites, and with Abraham himself, and with Isaac, and Jacob, who represented the things of love and faith. Likewise the high priests and priests, whatever their character, even those that were wicked, could represent the heavenly and most holy priesthood. In representatives the person is not regarded, but the thing that is represented. Thus all the kings of Israel and of Judah, even the worst, represented the royalty of the Lord; and even Pharaoh too, who set Joseph over the land of Egypt. From these and many other considerations-concerning which, of the Lord’s Divine mercy hereafter-it is evident that the covenants so often entered into with the sons of Jacob were only religious rites that were representative.