Sayyidah Umm Salamah (may Allah be pleased with her) says: I said: O Messenger of Allah (peace and blessings be upon him)! I braid the hair of my head tightly; should I undo the braids for the ritual bath for janabah (major impurity)? He (peace and blessings be upon him) said: "No, it is enough for you to pour three handfuls over it, then pour water over yourself and attain purity", or he said: "Then you will have become pure."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 843