The term "kitāb" (كتاب) in the context of Surah 2, Ayah 2 refers to the Qur'an itself.

Linguistically, "kitāb" derives from the root ك-ت-ب (k-t-b), which signifies writing, compiling, or prescribing. In Arabic, it can denote a written document, a book, or a decree. Its form here, *al-kitāb* (الْكِتَابُ), with the definite article, emphasizes its specific identity as *the* Book, i.e., the Qur'an.

Tafsir Ibn Kathir consistently identifies "al-kitāb" in this verse as the Qur'an. This interpretation is supported by the consensus of early scholars like Ibn `Abbas, Ibn Mas`ud, Mujahid, and Qatadah. The phrase "لَا رَيْبَ فِيهِ" (no doubt in it) further confirms its divine origin and authenticity as a revealed scripture.

The Qur'an itself uses "kitāb" in various contexts. For instance, in Surah 41:44, it states, "Say: It is for those who believe, a guide and a healing," referring to the Qur'an as "kitāb." Similarly, Surah 10:57 describes the Qur'an as "a good advice... and a healing... a guidance and a mercy for the believers."

Thus, "kitāb" here signifies the divinely revealed and compiled scripture, the Qur'an, which is free from doubt and serves as guidance.

📚 Sources: Classical tafsir (multi-source)