The Qedushah is called such by virtue of the word Qadosh, which begins the verse Holy, Holy, Holy, is the Lord of Hosts; the whole earth is full of His glory" (Isa. 6:3). It is the constant element of the liturgical Qedushah. Its various forms can be categorized by the additional verses. The forms of the Qedushah that appear in Qumran allude to the Isaianic verse without actually citing it. It appears in early Christianity as a single verse. It also appears in four rabbinic liturgies albeit not by itself. In the first blessing of the Shema (Qedushah de-Yoser), in the third blessing of the daily and holiday Amidah, the Sabbath Musaf, and in Uva Le-Tsion (Qedushah De-Sidra). They differ in their prologue and in their number of verses. The Shema version contains two verses, the Amidah three, the Musaf four and Qedushah De-Sidra three with an expansive Aramaic translation. Each contains connecting material between the verses. The order of the verses are about the same. When there are two, they are Isa. 6:3 and Ezek. 3:12 -- "Blessed be the glory of the Lord from its place." When there are three, the third is either Ps. 146:10 -- "May the Lord reign forever; your God, O Zion throughout all generations," or Ps. 15:15 -- "May the Lord reign forever and ever." When there are four, the added verse is the Shema inserted between the second and the third.
The fact that Isa. 6:3 is alluded to in the Dead Sea Scrolls, and appears in early Christianity and elsewhere all without Ezek. 6:3 attests to the absence of a necessary connection between them. Since Ezek. 6:3 was understood by the rabbis as attesting to angelic ignorance of the place of the Divine, it was added to the liturgy to downgrade the angels and to upgrade an Israel who does know where it is as evidenced by their saying the Shema.
Since the first blessing of the Shema has an antecedent at Qumran with an allusion to Isa. 6:3, it appears that the rabbis inserted Ezek. 6:3 into this blessing to promote their position of the superiority of Israel over the angels.