The Day is an object, meaning: So how will you protect yourselves on the Day of Resurrection when it is for Him, if you remain in disbelief. And you did not believe and do good deeds. It is permissible that it is a time indicator, meaning: So how will you have piety on the Day of Resurrection if you disbelieved in this world. It is permissible that it is in the accusative case with 'you disbelieved' interpreted as 'you denied,' meaning: So how will you fear Allah and be in awe of Him if you denied the Day of Resurrection and the recompense: for the piety of Allah is the fear of His punishment. It makes the children’s hair turn gray, as a metaphor for severity. It is said on a severe day: a day that makes the forelocks of children turn gray. The origin of it is that when worries and sorrows intensify upon a person, gray hair appears quickly. Abu al-Tayyib said: 'And worry cuts down the stout man to thinness... and makes the forelock of the boy gray and ages him.' [Abu al-Tayyib says: worry diminishes the stout man and cuts him down little by little. Thinness is a noun of the same meaning, as it corresponds to respect in meaning. It is permissible that it is a distinguishing feature, meaning: great worry diminishes the stout man in terms of thinness that arises from it. It is also permissible to consider it an object for a reason according to the view of those who do not condition the unity of the action and the source in the subject. The forelock is the front of the head, meaning: the boy’s head turns gray. The forelock is specified because it is what faces the observer when facing each other, and there is no hair of the boy except on his head, and he ages, meaning: the boy becomes weak and aged.] It has been reported to me in some books that a man went to bed with black hair like the beak of a raven, and woke up with a white head and beard like the thigama plant. He said: 'I saw the Resurrection, Paradise, and Hell in a dream, and I saw people being led in chains to the Fire. From the horror of that, I woke up as you see.' It is permissible to describe the day as long. And that children reach the age of old age and gray hair in it. The sky is split by it, a description of the day in terms of severity as well. And that the sky, despite its vastness and strength, splits in it, so what do you think of other creatures? It has been recited: 'split' and 'bursting.' The meaning is: having a split. Or interpreted as the sky being the ceiling. Or interpreted as the sky being something that splits, and the 'by it' is like in your saying: 'I split the wood with the axe,' meaning: it splits due to the severity of that day, as something splits by what splits it. It is permissible that the sky is heavy with it, a heaviness that leads to its splitting due to its greatness upon it and its fear of its falling, like His saying: 'It has become heavy in the heavens and the earth.' His promise is from the addition of the source to the object, and the pronoun refers to the day. It is permissible that it is added to the subject, which is Allah, the Exalted and Majestic, and there is no mention of Him because His knowledge is known.