Life on other planets

Imam Sadiq (peace be upon him) has said:
“Surely Allah has created twelve thousand worlds, each of those worlds is greater than the seven heavens and the seven earths. None of (those) worlds thinks that Allah has got any other world (than them), and I am Allah’s Huja (guardian) over them."

(al-Bihar Chapter 15, Hadith no. 1)

Imam Muhammed al-Baqir (peace be upon him) has said:

"Surely Allah had created in the earth - since He created it - seven worlds; they (the creatures who live on it) were not from the children of Adam; He created them from the surface of the earth, then He placed them on it one after another with its world. Then Allah, the Mighty, the Great, created Adam, the father of mankind, and created his progeny from him”

(al-Bihar Chapter 28, Hadith no. 1)

Jaber bin Yazid has once said (what it means):
“I asked Abu Jafar (peace be upon him) about the verse:
“Were We then fatigued with the first creation? Yet are they in doubt with regard to a new creation” (50:15)
Then He said: Oh Jabir the interpretation of this verse is that when Allah the Most Exalted has ceased this creation and this world to exist, and dwelt the people of paradise in paradise and those of hell fire in hell fire, Allah will create a new world other than this world, and new creation (without reproduction) to worship and glorify Him, ……. Do you suppose that Allah has created this single world and He has not created any other beings apart from you. Yes, by Allah, He has created a thousand thousand worlds and a thousand thousand Adams and you are in the last of those worlds.”

(al-Bihar Chapter 28 Hadith no. 2)