Musannaf Ibn Abi Shayba 1:776

Hafs narrated to us, from al-A'mash, from Ibrahim, who said: Abdullah said: "If the *junub* (person in a state of major ritual impurity) washes his head with *khatmi* (marshmallow plant), that suffices him." Ibrahim said: "He said the same," or he said: "He does not repeat [the washing] upon it."