Tafsir of Al-Mursalat 77:9

It means it is split (shuqqat), as He, the Exalted, said: "When the sky has split asunder" (Inshiqaq: 1) and "And [mention] the Day when the heaven will split open with [emerging] clouds" (Furqan: 25). It has also been said that it means opened (futihat), as He, the Exalted, said: "And the heaven will be opened and will become gateways" (Naba: 19). Sibawayh recited: "The gate of the amir is shut (al-farji)." There is no impediment to this either, whether the sky is a solid body or a subtle body, and the arguments for the impossibility of cleaving and healing within it are ruptures that do not heal.