Tafsir of Al-Haqqah 69:16

And the heaven will split asunder: It will crack and separate, and parts of it will become distinct from others. Perhaps this is an indication of what is contained in His saying, the Exalted: "The day the heaven will split asunder with clouds and the angels will be sent down in successive descent." Ibn al-Mundhir recorded from Ibn Jurayj that he said: "That is [the meaning of] His saying, the Exalted: 'And the heaven will be opened and will become gateways.'" There is no contradiction between them, just as there is no contradiction between the splitting being for the descent of the angels and its being due to the terror of the Day of Judgment; for a matter may have various causes such as these. The intended meaning of "the heaven" is its genus, though it has been said that it refers to the seven heavens. Regardless, it is not a condition for the validity of "splitting" that they be solid bodies, as the term can be applied to what is not solid; for instance, the sea has been described as having "split" (infalaq).

For it: That is, the heaven.

On that day is frail: Meaning weak, derived from wahiya (the thing became weak and prone to falling). Ibn Shajara said regarding the derivation: "It is from the saying: 'The water skin became wahiya'—meaning it tore." Among their proverbs is the saying of the Rajaz poet:

Leave the way of one whose water skin has torn, And whose water has been spilled in the wilderness.