Mu'awiyah ibn Hakim narrated from Ibn Al-Mughira, from Muthanna ibn Abd Al-Salam, from Abu Abdullah عليه السلام. He said: I said to Imam عليه السلام: "I scratched my skin, and blood came out." Imam عليه السلام said: "If it gathers to the size of a lentil (hummus seed), then wash it. Otherwise, you do not need to wash it."