Fiqh-us-Sunnah Volume 1, Purification and Prayer, Fiqh 1.002C.

This category refers to water which drips from the person after he performs ablution or ghusl. It is considered pure because it was pure before its use for ablution, and there is no basis to think that it has lost its purity. This statement is supported by the hadith of Rab’i bint Mu’wazh which describes the ablution of the Messenger of Allah. She states, “He wiped his head with (the water) remaining on his hands from his ablution.” This hadith is related by Ahmad and Abu Dawud. Abu Dawud’s version is, “The Messenger of Allah, upon whom be peace, wiped his head with the extra water that was in his hand.” Abu Hurairah also reported that the Messenger of Allah met him alone in the streets of Madinah while he was in post-sex impurity. He therefore slipped away, made ghusl and returned. The Messenger of Allah, upon whom be peace, asked him “Where have you been, Abu Hurairah?” He answered, “I was in post-sex impurity and did not want to sit with you while I was in that condition.” The Prophet replied, “Glory be to Allah. The believer does not become impure.” This is related by “the group.”

This is based on the rationale that since a believer never becomes impure, the water he uses for purification also does not become impure. Thus, a pure object touching a pure object cannot result in one’s becoming impure. Ibn al-Munzhir said that it is related that ‘Ali, Ibn ‘Umar, Abu Umamah, ‘Ata, al-Hassan, Makhul and anNakha’i said that if a person forgot to wipe his head while making ablution, it is sufficient for him to wipe his head with any water remaining in his beard. Ibn al-Munzhir stated that this proves that they took “used water” as pure. This opinion comes from one of the narrations attributed to Malik and ash-Shaf’i. Ibn Hazm ascribes it to Sufyan al-Thauri, Abu Thaur, and all scholars of the Zhahiri school of thought.