Is it true that words not containing a a labial consonant are foreign (non-Arabic), and does this apply to words like "ḥayāh" (life) and "Yaḥyā" (John the Baptist) in the Holy Quran?

"Dhalāqah" is a characteristic of certain letters: Fāʼ, Rāʼ, Mīm, Nūn, Lām, and Bāʼ. These are called "al-ḥurūf al-mudhlaqah" or "ḥurūf al-idhlaq." They are named so due to their lightness and the speed with which they are pronounced. Some of them emanate from the "dhalq" (tip) of the tongue, and others from the "dhalq" of the lips.

It is not true that words lacking a "mudhlaq" letter are foreign (non-Arabic). Rather, it is rare for a quadriliteral or quinqueliteral verb to be devoid of one of these letters. Scholars have clarified that the best constructions result from the combination of diverse letters. There is no quadriliteral construction with "solid" (non-dhalāqah) letters that does not include "dhalāqah" letters, except for a construction that includes the letter Sīn, which is very rare, such as "ʿasjad." The "dhalāqah" letters are the lightest in pronunciation, the most frequent in speech, and the best for word construction. The construction of a complete quadriliteral or quinqueliteral word is not good unless some of these letters are included, such as: "Jaʿfar," "Dardaq," "Safrajal," and "Dardabīs." As for the words of the Quran, they are of the highest eloquence and beauty, and contain no rare or anomalous styles.