Muwatta Malik #756

Yahya related to me from Malik from as-Salt ibn Zubayd from more than one of his family that Umar ibn al-Khattab discovered the smell of perfume while he was at ash-Shajara. Kathir ibn as-Salt was at his side, and Umar asked, "Who is this smell of perfume coming from?", and Kathir said, "From me, amir al-muminin. I matted my hair with perfume and I intended not to shave it.'' Umar said, "Go to a sharaba and rub your head until it is clean," and Kathir did so. Malik explained, "A sharaba is the ditch at the base of a date-palm."