Law arada Allahu an yattakhitha waladan lastafa mimma yakhluqu ma yashao subhanahu (surah Zumar: 4)

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

(39:4) If Allah had wanted to take to Himself a son, He could have chosen anyone He wanted out of those whom He creates. *8 Glory be to Him (that He should have a son). He is Allah: the One, the Overpowering. *9

Law araadal laahu aiyattakhiza waladal lastafaa mimmaa yakhluqu maa yashaaa`; Subhaanahoo Huwal laahul Waahidul Qahhaar

*8) That is, "It is just impossible that Allah should havc begotten a son. The only possibility is that Allah should choose someone for Himself; and whomever He chooses will inevitably be from among the creatures, for everything in the world, apart from Allah, is His creation. Now, evidently, however exalted and chosen a creature might be, it cannot havc the position of the offspring. For between the Creator and the created there exists a great disparity of nature and essence and character, and parenthood necessarily demands that there should be the unity of nature and essence between a father and his offspring." Besides, one should also bear in mind the point that the words: "Had Allah willed to take a son, He would......" themselves give the meaning that Allah has never willed so. Here the object is to impress that not to speak of taking a son, Allah has never even willed so.
*9) The following are the arguments by which the doctrine of parenthood has been refuted: First, that Allah is free from every defect and fault and weakness. Obviously, children are nee ded by the one who is defective and weak; the one who is mortal stands in need of them, so that his progeny should continue to live after him in the world. Likewise, he who adopts a son does so either because he feels the need of having an heir, being childless himself, or he adopts a son being overpowered by love of somebody. Attributing such human weaknesses to Allah and forming religious creeds on their basis is nothing but ignorance and shortsightedness. The second argument is that Allah in His essence and Being is unique: He is not a member of a species, whereas, evidently, offspring must necessarily belong to a species. Furthermore, there can be no concept of offspring without marriage, and marriage can take place only between homogeneous individuals. Therefore, the one who proposes offspring for the Unique and Matchless Being like Allah, is ignorant and foolish: The third argument is that Allah is Omnipotent, i.e. whatever is there in the world is subdued to Him and is held in His powerful grasp. No one in this Universe has any resemblance with Him in any way or degree on account of which it may be imagined that he has some relation with Allah.