Sunan Ibn Majah 339

It was narrated from Ya'la bin Murrah that his father said:"I was with the Prophet on a journey, and he wanted to relieve himself. He said to me: 'Go to those two small date-palm trees and tell them: "The Messenger of Allah orders you to come together.'" So they came together and he concealed himself behind them, and relieved himself. Then he said to me: 'Go to them and tell them: "Go back, each one of you, to your places.'" So I said that to them and they went back