«مطلع» with a fathah (is a masdar) meaning "rising."
«مطلع» with a kasrah on the laam (as Kisai has recited) means the place from where the sun rises.
In «انا أنزلناه‏» , the pronoun refers to the Qur'an (even though the Qur'an has not been mentioned above, but for the sake of its honor, the pronoun is used before its mention).
«أنزلناه‏» is in the plural form of the first person, even though the one who sends down (the revelation) is only one, that is, Allah the Exalted. But in Arabic, the singular is sometimes expressed in the plural form «جميع» and for affirmation, the plural form is used.

The meaning of «منفكين‏» is "one who abandons." «قيمة‏» is firm and strong, although "deen" (religion) is masculine, it has been attributed in the feminine form, that is, as «قيمة‏» . "Deen" has been taken in the meaning of "millat" (community/faith), which is feminine.

Narrated Anas bin Malik: The Prophet said to Ubai (bin Ka`b). "Allah has ordered me to recite to you:--'Those who disbelieve among the people of the Scripture and among the idolators are not going to stop (from their disbelief.') (Sura 98) Ubai said, "Did Allah mention me by name?" The Prophet said, "Yes." On that, Ubai wept.