In the name of Allah the Beneficent the Merciful
Sayings of Prophet Muhammad PBUH about the seven skies from Sahih Bukhari and (Muslim)
"It is He Who hath made you (His) agents, inheritors of the earth: He hath raised you in ranks, some above others: that He may try you in the gifts He hath given you: for thy Lord is quick in punishment: yet He is indeed Oft-forgiving, Most Merciful" (Al-An'âm 6: 165)