Zamzam is the name of a famous well in al-Masjid al-Haraam [the Sacred Mosque in Makkah], which is thirty-eight cubits away from the Ka'bah. It is the well from which Allah quenched the thirst of Ismaa'eel the son of Ibraaheem (A.S) when he was an infant. His mother Haajra (A.S) looked for water for him, but could not find any. She climbed to the top of Mount al-Safaa, praying to Allah to help her and give her water for Ismaa'eel, and then she climbed to the top of Mount al-Marwah and did the same. Allah sent Jibreel (A.S), and he struck the earth, and water appeared.
The scholars agreed that it is mustahabb (recommended) for pilgrims on Hajj and 'Umrah in particular, and for all Muslims in general, to drink Zamzam water, because of the saheeh hadeeth in which Nabi (S.A.W) is reported to have drunk the water of Zamzam. (al-Bukhaari).
According to the hadeeth of Abu Dharr (R.A), Nabi (S.A.W) said concerning the water of Zamzam "It is a blessing, and it is food that satisfies." (Muslim).
Al-Tayaalisi added, in a version that he narrated: "and a cure for the sick. – but this is when he drinks it with faith and sincerity, as proven in the hadeeth of Abu Dharr al-Ghifaari who stayed in Makkah for a month without any nourishment except Zamzam water.
Ibn al-Mubaarak entered Zamzam and said,
"O Allah, Ibn al-Mu'ammal told me, from Abu'l-Zubayr from Jaabir that the Messenger of Allah (peace be upon him) said: 'The water of Zamzam is for whatever purpose it is drunk for,' so, O Allah, I am drinking it (to quench) my thirst on the Day of Resurrection.
The Prophet (peace and blessings of Allah be upon him) said: "The best water on the face of the earth is the water of Zamzam; it is a kind of food and a healing from sickness." (Saheeh al-Jami).
The Messenger of Allah (peace and blessings of Allah be upon him) said: "The water of Zamzam is for whatever it is drunk for." (Ibn Majah)
The Messenger of Allah, sallallahu alayhi wa salam has said:" The most sublime of all earthly waters is that of Zamzam; therein one finds food for the hungry and medicine for the ill." [At- Tabaraani]
"Zamzam water is what one intends to drink it for. When one drinks it to be healed, Allah heals him; when one drinks it to be full, Allah makes him full; and when one drinks it to quench his thirst, Allah quenches it. “[Ahmad and Ibn Majah]
Since Zamzam water serves whatever purpose and intention for which it is drank; provided it is with sincerity So next time when one gets the opportunity to drink Zamzam, one should grab the opportunity to pray for: a healthy body, sharp mind, forgiveness for sins, life in Jannah after death, an honorable death on the day of Jummah, and all one's physical and spiritual needs of this world and Hereafter.