Tafsir of Al-Waqi'ah 56:70

(Meaning): Salty and bitter, such that it cannot be drunk. It is derived from al-ajīj, which is the flaring of fire. It is also said: Al-ujāj is everything that stings the mouth and cannot be drunk, thus encompassing what is salty, bitter, and hot. Either that is intended, or specifically salty, due to the context.

The lam (the emphatic particle) was omitted from the apodosis of law (the conditional particle) here due to the verbal and situational context. If the omission of the lam is permissible in the saying of Aws: "Until when the dogs said to it..."—where the context is situational—then it is more fitting that its omission here be permitted for the same reason, as established by al-Zamakhshari.

He also proposed another view, the essence of which is that the lam is solely for emphasis, and therefore it suits the context of emphasis. It was included in the verse concerning food (in the previous verse) but not in the verse concerning drink (this verse), 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, since the drink follows the food. Do you not see that a guest is given drink after being fed? Physicians have mentioned that water is a digestive aid. This is supported by its [food] being mentioned before the drink in the Majestic Arrangement.

The Imam (al-Razi) has a lengthy discussion in this station in which he objected to al-Zamakhshari and explained the reason for its mention first and its omission second, but I have not seen him offer an explanation that satisfies the heart. Better than his view, in my opinion, is what Ibn al-Athir said in al-Mathal al-Sa’ir: "The lam was included in the food but not the drink because turning fresh water into salt water is easier in common custom and habit, and salty water exists in greater abundance than fresh water. Often, when fresh water flows over lands with changing soil compositions, they turn it salty. Thus, in turning fresh water into salt, there was no need for additional emphasis; hence, the emphatic lam, which conveys additional confirmation, was not included. As for food, making it hutaman (broken debris) is among the things that deviate from the ordinary, and when it occurs, it is out of severe wrath; therefore, it was conjoined with the lam to establish its creation and confirm its reality." End quote.

(It is) an incitement to give thanks for all of it, for it is more beneficial than the sweetness of the water alone, contrary to what some have suggested.

Yes, Ibn Abi Hatim recorded from Abu Ja’far—may Allah be pleased with him—that the Prophet—may Allah bless him and grant him peace—used to say when he drank water: "Praise be to Allah, who gave us fresh water to drink through His mercy, and did not make it salty and bitter due to our sins."