Tafsir of Al-Waqi'ah 56:68-70

If you ask: Why was the lam (particle of emphasis) included in the response to law (if) in His saying: {We would have made it debris} (Al-Waqi'ah: 65), yet it was removed here?

I say: Since law enters upon two sentences where the second is connected to the first by the connection of a consequence to a condition, and it is not purely conditional like in (if), nor does it function like it—rather, the meaning of the condition permeates it incidentally, in that it conveys that the second [event] was prevented by the prevention of the first—it required in its response something to serve as a sign of this connection. Thus, this lam was added to be a sign of that.

When it is omitted after having become a well-known sign, it is because when a thing is known, its position is famous, and it becomes familiar and accustomed, one does not mind dropping it from the wording, relying on the listener's knowledge. Do you not see what is narrated about Ru'bah, that he would say "Khayr" (Good) to someone who asked him, "How did you wake up?" He omitted the preposition (bi-khayr) because everyone knows its place. The state of its omission and its inclusion are equal due to the fame of the matter. Sufficient for you is the saying of Aws: Until, when the dogs said to her: Like today, neither sought nor seeking. (He omitted "I did not see"). Therefore, its omission is a verbal abbreviation, while it remains fixed in meaning. Thus, the two places are equal with no difference between them. Furthermore, the preceding mention of it, with the short distance [between the verses], makes mentioning it a second time unnecessary, acting as a substitute for it.

It is also permissible to say: This lam provides the meaning of emphasis without a doubt. It was introduced in the verse of food, but not in the verse of drink, to indicate that the matter of food takes precedence over the matter of drink, and that the threat of its loss is more severe and difficult, because drink is only needed as a consequence of food. Do you not see that you only give your guest a drink after you have fed him? If you were to reverse it, you would fall under the saying of Abu al-'Ala': If you serve the guests of people pure milk, They serve their guests cold, clear water. Some of the Arabs would drink and say: "I do not drink except upon a stomach that has food (thamila)." For this reason, the verse of food was placed before the verse of drink.