Asim bin Mundhir (may Allah have mercy on him) says that we were in our or Ubaidullah bin Abdullah bin Umar's (may Allah have mercy on him) garden when the time for prayer came. Ubaidullah got up and went to the pond in his garden and began to perform ablution, while there was a camel's skin lying in it. We said: You are performing ablution with this water, while this skin is lying in it. He said: My father told me that the Messenger of Allah (peace and blessings of Allah be upon him) said: If the water is two pitchers (or more), it does not become impure.