en_tn_condensed/isa/08/16.md

Bind up my testimony, seal the official record

These two phrases mean basically the same thing. Alternate translation: "Close up tightly the scroll with this message written on it" (See: rc://en/ta/man/translate/figs-parallelism)

my testimony ... my disciples

It is unclear to whom the word "my" refers. It could be Isaiah or Yahweh. It is best to leave the pronouns ambiguous if your language will allow it.