And indeed it is, in the Mother of the Book with Us, (43:4)

Almuntakhab Fi Tafsir Alquran Alkarim

And it is a transcript reflecting the grandeur of the archetypal Book in the heavens realm as held by Us in high esteem and a source of wisdom

Tafseer Tafheem-ul-Quran by Syed Abu-al-A'la Maududi

(43:4) Indeed it is transcribed in the Original Book with Us; *2 sublime and full of wisdom. *3

And indeed it is, in the Mother of the Book with Us, meaning

*2) "Umm al-Kitab": the "Original Book": the Book from which alI the Books sent down to the Prophets have been derived. In Surah AI-Waqi`ah the same thing has been described as Kitab-um-Maknun (the hidden and preserved Book) and in Surah AI-Buruj 22 as Lauh-i Mahfuz (the Preserved Tablet), that is, the Tablet whose writing cannot be effaced, which is secure from every kind of interference. By saying that the Qur'an is inscribed in Umm al-Kitab, attention has been drawn to an important truth. Different Books had been revealed by Allah in different ages to different Prophets for the guidance of different nations in different languages, but aII these Books invited mankind to one and the same Faith: they regarded one and the same thing as the Truth; they presented one and the same criterion of good and evil; they propounded the same principles of morality and civilization; in short, they brought one and the same Din (Religion). The reason was that their source and origin was the same, only words were different; they had the same meaning and theme which is inscribed in a Source Book with Allah, and whenever there was a need, He raised a Prophet and sent down the same meaning and subject-matter clothed in a particular diction according to the environment and occasion. Had Allah willed to raise the Prophet Muhammad (upon whom be His peace) in another nation instead of the Arabs, He would have sent down the same Qur'an in the language of that nation. In it the meaning and content would have been expressed according to the environments and conditions of the people and land; the words would have been different and the language also different but the teaching and guidance the same basically, and it would be the same Qur'an though not the Arabic Qur'an. This same thing has been expressed in Surah Ash-Shu`ara, thus: "This (Book) has been revealed by the Lord of the worlds. The trustworthy Spirit has come down with it upon your heart so that you may become one of those who are (appointed by God) to warn (the people) in plain Arabic language; and this is also contained in the scriptures of the former peoples." (vv. 192-196). (For explanation, see Ash-Shu`ara: 192196 and the E.N.'s on it).
*3) This sentence is related both to Kitab-i mubin and to Umm al-Kitab. Thus, it is in praise of boththe Qur'an and the Original Book from which the Qur'an has been derived. This praise is meant to impress the fact that if a person dces not recognize the true worth of this Book and dces not benefit from its wise teachings because of his own folly, it would be his own misfortune. If someone tried to degrade it and found fault with it, it would be his own meanness. It cannot become worthless on account of someone's lack of appreciation of it, and its wisdom cannot be eclipsed by anyone's throwing dust at it. This is by itself a glorious Book, which stands exalted by its matchless teaching, miraculous eloquence, faultless wisdom and the sublime personality of its great Author. Therefore, none can succeed in minimizing its value and worth. In verse 44 below the Quraish in particular and the Arabs in general have been told that the revelation of the Book for which they are showing such lack of appreciation had provided them a unique opportunity of honour, which if they lost, would subject them to a severe accountability before God. (Please see E.N. 39 below).
 

And indeed it is, in the Mother of the Book with Us, meaning in Urdu

اور در حقیقت یہ ام الکتاب میں ثبت ہے، ہمارے ہاں بڑی بلند مرتبہ اور حکمت سے لبریز کتاب