And hasten to forgiveness from your Lord and a garden as wide as the heavens and earth, prepared for the righteous
The following excerpt is taken from “Anwar al Bayan” vol 1 pg. 444-445:
“Hasten to the forgiveness f your Lord and that Heaven (Jannah)…” Since man has only the expanse of the heavens and the earth before him, this example is cited so as to make it easy for him to understand (Ruhul Ma’ani v.4 p.56). In actual fact, Heaven (Jannah) is much larger than this, as the Holy Prophet (peace and blessings of Allah be upon him) mentioned in a hadith that the Heaven (Jannah) of the last person to enter shall be ten times larger than this world, and more. (Mishkatul Masabih v 2 p 492)
The Being who has created the heavens and the earth is perfectly Capable of creating things much larger. People have hardly reached the limits of the heavens, but having seen the earth, they say that they cannot see that which the Quran and Ahadith speak of. At the outset, it should be understood that they have not necessarily explored the entire earth. Even if they had done so, there still exists another six of these earths and heavens. Between each of these are distances unimagined, and no one can even hope to get close to the sun! It is therefore sheer ignorance to claim that they have searched the universe thoroughly and can still not find Heaven (Jannah) and Hell. They have not even explored the visible heavens and earth, how can they be expected to find what is beyond these?
The author of “Ma’alimut Tanzil” (v. 1 p. 351) writes that the verse mentions the wird “arduha” (“the expanse of which”) which really refers to the width and breadth of Heaven (Jannah). It can be noted from this that the length is even vaster.
A person once asked Sayyidina Anas (May Allah be pleased with him) whether Heaven (Jannah) was in the skies or in the earth. He replied, “Which skies and earth can possibly accommodate Heaven (Jannah)?” It was then asked where is it then. He said, “It is above the seven heavens and beneath the throne of Allah. Sayiddina Qatada (May Allah be pleased with him) says that the Companions (Sahaba) (may Allah be pleased with him) and their descendants knew that Heaven (Jannah) lay above the seven skies and below the divine throne, while Hell lay beneath the seven earths.
Madani, Muhammad. Anwar ul Bayan. (p. 444-445). http://www.islamicweblibrary.com/wp-content/uploads/2020/04/Tafsir-Anwarul-Bayan-01.pdf