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"The apostles didn't consider themselves to be writing scripture. To them Tanakh were the only scripture there were."

Yet the Apostle Peter specifically referred to the letters of the Apostle Paul as scripture.

[editor-surveyor]

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Actually, the early copies of Peter’s epistle do not indicate “other scriptures,” but simply “scriptures,” so the “other” was obviously added centuries after peter wrote his letter.

No, the apostles were not arrogant enough to assume their letters were “scripture,” Tanakh was “Holy” (set apart) to them.
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