The King James translators added two insignificant words to the text (vv. 12–14). These are also difficult verses, however, the Book of Mormon helps. Apparently the Lord had forbidden Isaiah to preach unto Israel and Judah (v. 11) as Mormon was forbidden to preach to the Nephites:
16 And I did endeavor to preach unto this people, but my mouth was shut, and I was forbidden that I should preach unto them; for behold they had wilfully rebelled against their God; and the beloved disciples were taken away out of the land, because of their iniquity. [Mormon 1:16]
However, Mormon was to “stand as an idle witness to manifest unto the world the things which [he] saw and heard, according to the manifestations of the Spirit which had testified of things to come” (Mormon 3:16). Isaiah’s situation was similar. The Lord had left Israel and Judah without excuse by giving her two or three witnesses. The first was the sign given to Ahaz (Isaiah 7:14). The second sign was the great roll that Isaiah wrote upon. Two faithful witnesses also attested to the writing on the roll, Uriah and Zechariah (vv. 1–2). The third witness was the name of the son of Isaiah, Maher-shalal-hash-baz (destruction is imminent) (v. 3). Isaiah was to sanctify the Lord of Hosts and to fear him (v. 13); the Lord would then be his sanctuary. However, the Lord would be a stumbling block to both the unbelieving houses of Israel (v. 14).
To those disciples who would hearken, Isaiah was to “bind up the testimony” and “seal the law” (v. 16). Prophets both ancient and modern are given power to bind and seal something on earth and have it sealed in heaven. Peter was given “the keys of the kingdom: and whatsoever thou shalt bind on earth shall be bound in heaven: and whatsoever thou shalt loose on earth shall be loosed in heaven” (Matt. 16:19; see also 18:18). Modern-day servants had “power given [to them] to seal both on earth and in heaven” (D&C 1:8; see also 68:12). While the sealing may be a sealing unto heaven or a sealing against heaven, as shown in the various references cited, Isaiah was charged to seal up the disciples to heaven. Isaiah attested that he would follow the Lord’s directions, and wait for further instructions (v. 17). He further acknowledged that he and his children (through their names) were witnesses of the Lord to Israel (v. 18).