Abu al-Zubayr (may Allah have mercy on him) said: We were with Sayyiduna Jabir bin Abdullah (may Allah be pleased with them both), talking, when the time of the Asr prayer came. He stood and led us in prayer in a single garment wrapped around his neck and chest, while his cloak lay set aside. Then some Zamzam water was brought to him, and he drank, then drank again. They asked: "What is this?" He said: This is Zamzam water, and about it the Messenger of Allah (peace and blessings be upon him) said: "Zamzam water is for whatever it is drunk for." He said: Then the Prophet (peace and blessings be upon him), while he was in Madinah before Makkah was conquered, sent word to Suhayl bin Amr (may Allah be pleased with him): "Send us some Zamzam water as a gift, and do not neglect it." So he sent him two large water-skins.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 9987