Tafsir Al-Jalalayn: Al-Haaqqa, Ayah 39

And all that ye see not) O people of Mecca; it is also said that this means: I swear by what you see, i.e. the sky and the earth, and that which you do not see, i.e. the Garden and the Fire; and it also said that this means: I swear by what you see, the sun and the moon, and by that which you do not see, the Throne and the Stool; and it is also said that this means: I swear by what you see, i.e. Muhammad (pbuh) and that which you do not see, Gabriel. Allah swore by all these.