וַ֠יִּקֹּב בֶּן־הָֽאִשָּׁ֨ה הַיִּשְׂרְאֵלִ֤ית אֶת־הַשֵּׁם֙ וַיְקַלֵּ֔ל וַיָּבִ֥יאוּ אֹת֖וֹ אֶל־מֹשֶׁ֑ה וְשֵׁ֥ם אִמּ֛וֹ שְׁלֹמִ֥ית בַּת־דִּבְרִ֖י לְמַטֵּה־דָֽן׃
И сын израильтянки поносил Имя и проклял; и привели его к Моисею. И его мать'имя было Шеломит, дочь Дибри, из колена Дана.
Rashi
ויקב — Translate this as the Targum does: ופרש “and he pronounced”, thus ויקב … ויקלל means that he uttered the Tetragrammaton and by so doing blasphemed. It was the “Proper Name” which he had heard on Mount Sinai (cf. Sifra, Emor, Section 14 2 and Jeremiah Targ.).
Ibn Ezra
he pronounced Some translate this word to mean “uttered”, as in “which the mouth of God shall express” [Isaiah 62:2] and “as specified by name” [Numbers 1:17]. Others render it along the lines of “How shall I curse” [Numbers 23:8]. The former explanation strikes me as more plausible.
Rashbam
ויקוב, he mentioned the holy name of G’d before cursing same.