Al-Darawardi likewise transmitted it through the nephew of Ibn Shihab, from his father, from Anas, with the same wording. (1)

[The narration of Ibn ʿUmar (may Allah be pleased with him)]
Ahmad said: ʿAli ibn Hafs narrated to us; Warqaʾ informed us. He said: ʿAtaʾ related from Muḥārib ibn Dithār, from Ibn ʿUmar, who said: The Messenger of Allah ﷺ declared,

“Al-Kawthar is a river in Paradise. Its banks are of gold, and its water flows over pearls; it is whiter than milk and sweeter than honey.”

Ismaʿil ibn ʿUlayyah and Muḥammad ibn Fuḍayl also reported—from ʿAtaʾ ibn al-Saʾib, from Muḥārib, from Ibn ʿUmar—in a marfūʿ tradition:

“Al-Kawthar is a river in Paradise; its banks are gold, its bed is pearls and rubies, its soil more fragrant than musk, and it is whiter than snow.”

In another wording:

“Whiter than milk, sweeter than honey, and softer than butter.”

Al-Tirmidhi and Ibn Mājah likewise recorded it through the ḥadith of Muḥammad ibn Fuḍayl, and al-Tirmidhi said: It is ḥasan ṣaḥīḥ. (2)

[The narration of Ibn ʿAbbās (may Allah be pleased with him)]
Al-Bukhari said: Yaʿqūb ibn Ibrāhīm narrated to us; Hushaym narrated to us; Abū Bishr narrated to us, from Saʿīd ibn Jubayr, from Ibn ʿAbbās, who said concerning al-Kawthar, “It is the abundant good that Allah granted him.”

Abū Bishr said: I asked Saʿīd ibn Jubayr, “Some people claim that it is a river in Paradise.” He replied, “The river that is in Paradise is part of the abundant good that Allah granted him.” (3)

Ibn Jarir likewise reported—from Abū Kurayb, who said: ʿUmar ibn ʿUbayd narrated to us, from ʿAṭāʾ, from Saʿīd ibn Jubayr, from Ibn ʿAbbās—who said: “Al-Kawthar is a river in Paradise; its banks are gold and silver, it flows over rubies and pearls, and its water is whiter than snow and sweeter than honey.” Al-ʿAwfi also reported this from Ibn ʿAbbās.

[The narration of ʿĀʾishah (peace be upon her)]
Al-Bukhari said: Khālid ibn Yazīd al-Kāhilī narrated to us; Isrāʾīl narrated to us, from Abū Isḥāq, from Abū ʿUbaydah, from ʿĀʾishah—may Allah be pleased with her—who said: I asked her about the words of the Exalted, “Indeed, We have granted you al-Kawthar.” She answered, “It is a river that he was granted.”