ציטירנדיקער פּירוש אויף ישעיהו 27:7

And you shall make: Our predecessors said that the form of the keruvim were like two youths, and that its meaning is "like a baby (keravya)" in Aramaic, and that the [letter] kaf is [a prefix]. Yet they spoke correctly, that they have the form of children - if they have a tradition, and they made the word a mnemonic, like chanukah [is used]. For the kaf [in] keruv is [part of the] root. And the testimony ([is in] verse 20 of this chapter), "and hakeruvim were" - since the [letter] hay [at the beginning of the word (ha)] is a definitive hay and not one of questioning, like the hay (in Isaiah 27:7), "Was he beaten as his beater has been?" (Had the hay been used as a questioning hay, the kaf could have been part of the root.)