C. F. Keil and Franz Delitzsch on Isaiah 30:8

Isa 30:8

So runs the divine oracle to which the following command refers. “Now go, write it on a table with them, and note it in a book, and let it stand there fore future days, for ever, to eternity.” The suffixes of kothbâh (write it) and chuqqâh (note it) refer in a neuter sense to Isa 30:6, Isa 30:7; and the expression “go” is simply a general summons to proceed to the matter (cf., Isa 22:15). Sēpher could be used interchangeably with lūăch, because a single leaf, the contents of which were concluded, was called sēpher (Exo 17:14). Isaiah was to write the oracle upon a table, a separate leaf of durable material; and that “with them,” i.e., so that his countrymen might have it before their eyes (compare Isa 8:1; Hab 2:2). It was to be a memorial for posterity. The reading לעד (Sept., Targ., Syr.) for לעד is appropriate, though quite unnecessary. The three indications of time form a climax: for futurity, for the most remote future, for the future without end.