…he blasphemes Hashem…
Torah Temimah: Issi ben Yehudah vs Chachamim on megadef.
English: Our Rabbis taught: “He blasphemes Hashem” — Issi ben Yehudah says: like a person who says to his fellow, You have scraped the bowl and diminished it; and the Sages say: the verse comes only to assign kares to one who blesses the Name.
Meaning of megadef.
The Sages read megadef as actual blasphemy of the Name, which carries kares.