What is the prayer that Anas bin Malik was grieving over not being offered correctly according to the Prophet Muhammad (saw)?
      Narrated Az-Zuhri that he visited Anas bin Malik at Damascus and found     him weeping and asked him why he was weeping. He replied, "I do not      know anything which I used to know during the life-time of Allah's      Apostle except this prayer which is being lost (not offered as it      should be)."