لَيْسَ كَمِثْلِهِ شَيْءٌ
Nothing is like Him.
One rhetorical account understands the negation of likeness through an intensified form: denying anything comparable even to a supposed like reinforces, a fortiori, the denial of likeness to the referent Himself.
Another well-known grammatical account treats the kāf as additional for emphasis. The kināyah discussion focuses on a reading in which the kāf retains its ordinary function and the implication itself supplies force. The two analyses should not be treated as identical.