It is narrated from Sayyiduna Ibn Abbas (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) said: "The price of a dog is impure, and it (the dog) is more impure than it (the price)." All the narrators of this hadith are trustworthy (thiqah). If it is free of (weakness from) Yusuf bin Khalid al-Samti, then it is sahih (authentic) on the condition of Imam Bukhari. I have mentioned it because of the need for it, since the two Shaykhs have used the like of it in many places.