[Explanation]
The compiler—may Allah have mercy on him—cited this ḥadith in his Riyāḍ al-Ṣāliḥīn, near the close of the book among the miscellaneous narrations. It is related from ʿUqbah ibn ʿĀmir (may Allah be pleased with him) that the Prophet ﷺ went out to (the battlefield of) Uḥud and “prayed” over the martyrs there—that is, he supplicated for them; the formal funeral prayer is not intended, as the compiler himself made clear, for the well-known funeral prayer is offered before burial, not afterwards, except in the case of someone who missed the prayer prior to burial and makes it up later. Here, then, “prayer” means supplication, just as in the verse: “Take alms from their wealth to purify and cleanse them thereby, and pray for them” (Qur’an 9:103), i.e., invoke blessings for them.

After that, the Prophet ﷺ ascended the pulpit and addressed the people as though bidding them farewell. He told them that he could actually see his Basin: its water is whiter than milk, sweeter than honey, and more fragrant than musk, while its drinking vessels are as numerous and as radiant as the stars in the sky. On the Day of Resurrection people will arrive at that Basin parched from the length of their standing; the believers will drink from it—may Allah, out of His bounty and grace, include us and you among them—whereas the disbelievers will be driven away.

Therefore, whoever drinks from his teaching in this world, follows his sunnah, and traces his footsteps may rejoice, for he will drink from that Basin on the Day of Resurrection. But whoever fails to do so will be barred from it—Allah’s protection be sought. The Messenger of Allah ﷺ used to say that he could see his Basin even now; it had been unveiled to him in this world, just as Paradise and Hellfire were unveiled to him during the eclipse prayer. These are matters of the unseen; we do not know their precise reality, but Allah and His Messenger know best. What concerns us is to believe and affirm. On the Day of Resurrection people will approach the Basin and drink from it—except those who transgress.