(Isa. 8:16; D&C 88:84; 109:46; 133:71–72)
The threatened disaster predicted by Isaiah (the invasion of Syria and Israel) having taken place, and other prophecies having been partly fulfilled, the prophet finds himself vindicated by events. The meaning of these events, like a document legally drawn up and signed, is to be bound and signed in the hearts of his disciples.
(Sidney B. Sperry, Book of Mormon Compendium [Salt Lake City: Bookcraft, 1968], 204.)
One commentary indicates that the binding and sealing of the law is a symbolic process whereby one actually ties up a parchment roll, whereon the teachings of the prophets are recorded, as a witness against those to whom the message was delivered.
(J. R. Dummelow, as quoted in Hoyt W. Brewster, Jr., Isaiah Plain and Simple [Salt Lake City: Deseret Book Co., 1995], 81.)
Prophets both ancient and modern are given power to bind and seal something on earth and have it sealed in heaven (see Matt. 16:19; 18:18; D&C 1:8; 68:12). The wording of verse 16 is reversed in D&C 88:84, wherein the Lord sent his disciples among the Gentiles, and in the Appendix to the Doctrine and Covenants, referring to those who refused to believe in the Lord’s servants (see D&C 133:71–72). The wording therein is to bind up the law and seal up the testimony instead of binding the testimony and sealing up the law. However, the meaning is the same in either case. While the sealing may be a sealing unto heaven or a sealing against heaven, as shown in the various references cited, Isaiah’s charge was to seal up the disciples to heaven.
(Monte S. Nyman, Great Are the Words of Isaiah [Salt Lake City: Bookcraft, 1980], 65.)