whatever the Arabs classify as a ḥarf, the grammarians still call a kalimah. Thus they speak of Zayd and ʿAmr, and likewise of verbs such as qaʿada (sat) and dhahaba (went), as well as every particle that conveys a meaning while being neither noun nor verb, such as in (if), thumma (then), hal (the interrogative particle), and laʿalla (perhaps).

The Exalted says:
“and to warn those who say, ‘Allah has taken a son’” (Quran, Al-Kahf 18:4),

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“they have no knowledge of it, nor did their forefathers. How grave is the kalimah that issues from their mouths!” (Quran, Al-Kahf 18:5).

Here He refers to the entire utterance as a kalimah.

He, Most High, also says:
“a parable: a good kalimah is like a good tree” (Quran, Ibrahim 14:24),

and that kalimah is the declaration: There is no god but Allah.

He says as well:
“To Him ascends the good kalim (word), and righteous deeds raise it” (Quran, Fatir 35:10),

and:
“Say, People of the Book, come to a kalimah that is just between us and you: that we worship none but Allah, that we associate nothing with Him, and that none of us take others as lords alongside Allah” (Quran, Al-ʿImran 3:64).