Halakhah zu Tehillim 18:21

One has to be very careful in the prayer of Minchah of the holy Shabbat, for it has [the potential for] many ascents upwards. And even though there are siddurim in which it is written "And who is like Your nation Israel?"--the main idea is that one must say "like Your nation, like Israel" [and not "like Your nation Israel"], and just as [the author] wrote in Shalmei Chagigah in the name of Rabbi Ya'akov Tzemach in Nagid UMitzvah, and so it is in the siddur of our master, Rabbi Shalom Shar'abi of blessed memory, which is found among us. And from the language of Sha'ar HaKavvanot [by Rabbi Chayyim Vital], which mentions "like Your nation Israel"--from this [citation] there is no proof in general. And I said, with the help of Heaven, that the language of "like Israel" is more correct, for in II Samuel 7[:23], it says "like Israel," and, in [I] Chronicles 17[:21], it says, "Israel," and therefore what our master Rabbi Ya'akov Tzemach of blessed memory well wrote is correct, that we must say "like Israel"--on account of this being a verse from Prophets. And like this, we have found the pronouncing of 'Migdol yeshu'ot malko' (II Samuel 22:51) in Birkat HaMazon, for on Shabbat, we say "Migdol," just as it is written in Prophets (II Samuel 22:51), and, on a profane day, "Magdil," just as it is written in Scriptures (Psalm 18:21).