Tafsir of Al-Ghashiyah 88:5

They are given to drink from an aniyah (boiling) spring, meaning it has reached its inaha—that is, its ultimate limit in heat, so it is extreme in its intensity. This is as stated in the words of the Exalted, "And between it and a boiling an [i.e., boiling water]," and this is the well-known interpretation. It has been narrated on the authority of Ibn Abbas, al-Hasan, and Mujahid. Ibn Zayd said: It means "present for them," derived from the saying "the thing has ana (arrived/appeared)," but this view is not held in high regard.