That which is called the witness of the Spirit, Rom. vi., is elsewhere in the New Testament called the seal of the Spirit, 2 Cor. i. 22, Eph. i. 13, and iv. 30, alluding to the seal of princes, annexed to the instrument by which they advanced any of their subjects to some high honour and dignity or peculiar privilege in the kingdom, as a token of their special favour. Which is an evidence that the influence of the Spirit of the Prince of princes, in sealing His favourites, is far from being of a common kind; and that there is no effect of God’s Spirit whatsoever which is in its nature more divine; nothing more holy, peculiar, inimitable, and distinguishing of divinity. Nothing is more royal than the royal seal; nothing more sacred, that belongs to a prince, and more peculiarly denoting what belongs to him; it being the very end and design of it to be the most peculiar stamp and confirmation of the royal authority. It is the great note of distinction, whereby that which proceeds from the king, or belongs to him, may be known from every thing else.
Jonathan Edwards, The Religious Affections, iii.i
High Plains Parson 