The Sahih al-Bukhari, a collection of prophetic traditions, or "hadith" by Muhammad al-Bukhari refers to a collection of Muhammad's opinions on medicine, by his younger contemporary Anas bin-Malik. Anas writes about two physicians who had treated him by cauterization and mentions that the prophet wanted to avoid this treatment and had asked for alternative treatments. Later on, there are reports of the caliph ʿUthmān ibn ʿAffān fixing his teeth with a wire made of gold. He also mentions that the habit of cleaning one's teeth with a small wooden toothpick dates back to pre-Islamic times.