ADHIKR

For the word “in It”, the Arabic word “Feehaa” is used in the female gender without using “Feehi” in the masculine gender. That is because not in the body of the Book, but in Adhikr, which is the Soul of the Book, upright contents of all previous Books revealed before from the  Lord are included, as told in verse 5:48. That means just like the Soul of all human beings is the same which is from Allah, the Soul of all Books is also the same. That is mentioned as “Al Kithab–the Single Book” as explained in verses 2:1-2. See explanation 2:285 and 16:43-44.