There were times when Muslims had to pay for drinking water, when made them very thirsty, there was one water well and it was owned by a jew person, that jew person sold water for very high price so it was very difficult for the Muslims... But our holy prophet Usman (R.A) bought the well for the people for a very high cost, but he let anyone take the water for free... Which is the reason that 9 muharram is a special day for us