We believe that there is a cistern for Prophet Muhammad (may Allah’s peace and blessings be upon him), which his Ummah will converge on. Allah, Exalted be He, says: {We have surely given you [O Prophet] Al-Kawthar.} [Surat al-Kawthar: 1]
Anas (may Allah be pleased with him) reported: One day as the Messenger of Allah (may Allah’s peace and blessings be upon him) was sitting amongst us, he dozed off, and then he raised his head smiling. We said: "What makes you smile, O Messenger of Allah?" He said: "A surah has just been revealed to me; and he recited: {We have surely given you [O Prophet] Al-Kawthar; so pray and sacrifice to your Lord alone. Indeed, the one who hates you is truly cut off} [Surat al-Kawthar: 1-3]. Then, he said: "Do you know what the Kawthar is?" We said: "Allah and His Messenger know best." He said: "It is a river which my Lord, Exalted and Glorified be He, has promised me, and there is an abundance of good in it. It is a cistern to which my Ummah will come on the Day of Resurrection, and its tumblers will be as numerous as the stars. A person will be turned away from among them. I will say: 'O My Lord, he is one of my Ummah!' Thereupon, He will say: 'You do not know what he newly introduced to the religion after you.'" [Narrated by Muslim (400)]
In another Hadīth, the Prophet (may Allah’s peace and blessings be upon him) said: "My Cistern would take a month's journey to cross it. Its water is whiter than milk, its smell is nicer than musk, and its drinking cups are as numerous as the stars of the sky; whoever drinks from it will never be thirsty." [Narrated by Al-Bukhāri (6579) and Muslim (2292)]
He (may Allah’s peace and blessings be upon him) also said: "My Cistern has its dimensions wider than the distance between Ayla and Aden, and its water is whiter than ice and sweeter than honey diluted with milk, and its cups are more numerous than the stars. Verily, I shall prevent people therefrom just as a man prevents the camels of the people from his fountain." They said: "O Messenger of Allah, will you recognize us on that day?" He said: "Yes, you will have distinctive marks which nobody among the nations will have; you will come to me with bright forehead and bright hands and feet on account of the traces of ablution." [Narrated by Muslim (247)]
And the Prophet (may Allah's peace and blessings be upon him) also said: "While I was sleeping, a group was brought close to me, and when I recognized them, a man came out from between me and them and said: 'Come along.' I asked: 'Where?' He said: 'To Hellfire, by Allah.' I asked: 'What is wrong with them?' He said: 'They turned apostate as renegades after you left.' Then behold! (Another) group were brought close to me, and when I recognized them, a man came out from between me and them and said: 'Come along.' I asked: 'Where?' He said: 'To Hellfire, by Allah.' I asked: 'What is wrong with them?' He said: 'They turned apostate as renegades after you left.' So, I did not see anyone of them escaping except a few who were like camels without a shepherd." [Narrated by Al-Bukhāri (6587)]
Anas (may Allah be pleased with him) reported: After the Prophet (may Allah's peace and blessings be upon him) was taken for the journey of Mi‘rāj (ascension) to the heaven, he said: "I came upon a river the banks of which were made of tents of hollow pearls. I asked: 'What is this, O Jibrīl?' He said: 'This is the river of Kawthar.'" [Narrated by Al-Bukhāri (4964)]