Again, this is straight from Massekhet Soferim, paragraphs 8 and 10; Paragraph 9 set out a congregational response which seems not to have been adopted; after the first verse the congregation would rise and say "Faithful are you "Lord" our God, and trustworthy are your words. O faithful, living, and enduring, may you constantly rule over us forever and ever." This response apparently was in use in antiquity - the Jews of the eastern diaspora would recite this while seated, the Jews of Eretz Yisrael would stand. This practice appears to have ceased during the Middle Ages (it is not in Amram's prayerbook of the 9th century although a phrase of it ["Trustworthy are you "Lord" our God, living and enduring forever", right after "words are true and just"] is in the "Mahzor Vitry ", (ca. 1100), but in the 18th century Rabbi Jacob Emden criticized its omission. The second half of the blessing echoes Isaiah 45:23 and 55:11.