When the Sahaabah (radhiyallahu ‘anhum) migrated to Madeenah Munawwarah, the water that was found in Madeenah Munawwarah was difficult for them to drink due it being bitter. However, there was a Jew who had a well of sweet water named Roomah, and he used to sell the water of this well to the Sahaabah (radhiyallahu ‘anhum).
Rasulullah (sallallahu ‘alaihi wasallam) asked the Sahaabah (radhiyallahu ‘anhum), “Who will buy the well of Roomah and donate it to the Muslims so that he will be equal to them in drawing its water, and he will receive a well in Jannah in exchange?” Hazrat ‘Uthmaan (radhiyallahu ‘anhu) went to the Jew who was the owner of the well and offered to purchase Roomah from him. However, the Jew refused to sell the entire well, and instead sold half of the well to Hazrat ‘Uthmaan (radhiyallahu ‘anhu) for twelve thousand dirhams. Hazrat ‘Uthmaan (radhiyallahu ‘anhu) immediately donated it to the Muslims, and then said to the Jew, “If you wish, we can hang two buckets (so that we can both use the well at the same time), or if you prefer, I will use it on one day and you will use it on the next day.” The Jew replied that he preferred to alternate days with Hazrat ‘Uthmaan (radhiyallahu ‘anhu).
Thereafter, when it was the day of Hazrat ‘Uthmaan (radhiyallahu ‘anhu), the Muslims would come to the well and draw sufficient water to last them for two days. Seeing that the Muslims were no longer buying water from him, the Jew said to Hazrat ‘Uthmaan (radhiyallahu ‘anhu), “You have spoilt my well (as I can no longer sell the water to people)! Buy the other half from me.” Hazrat ‘Uthmaan (radhiyallahu ‘anhu) thus purchased the other half of the well from him for eight thousand dirhams.
(Istee‘aab vol. 3 pg. 157)