Tafsir Al-Jalalayn: Al-Qalam, Ayah 1

And from his narration on the authority of Ibn 'Abbas that he said regarding the interpretation of Allah's saying (Nun): '(Nun) He says: Allah swears by the Nun, which is the whale that carries the earths on its back while in Water, and beneath which is the Bull and under the Bull is the Rock and under the Rock is the Dust and none knows what is under the Dust save Allah. The name of the whale is Liwash, and it is said its name is Lutiaya'; the name of the bull is Bahamut, and some say its name is Talhut or Liyona. The whale is in a sea called 'Adwad, and it is like a small bull in a huge sea. The sea is in a hollowed rock whereby there is 4,000 cracks, and from each crack water springs out to the earth. It is also said that Nun is one of the names of the Lord; it stands for the letter Nun in Allah's name al-Rahman (the Beneficent); and it is also said that a Nun is an inkwell. (By the pen) Allah swore by the pen. This pen is made of light and its height is equal to the distance between Heaven and earth. It is with this pen that the Wise Remembrance, i.e. the Guarded Tablet, was written. It is also said that the pen is one of the angels by whom Allah has sworn, (and that which they write (therewith)) and Allah also swore by what the angels write down of the works of the children of Adam,