I heard the Messenger of Allah ﷺ say, "Any woman who adds to her hair another's hair has only added to it falsely."
سمعت رسول الله ﷺ يقول: أيما امرأ- أدخلت في شعرها من شعر غيرها فإنما تدخله زورا.
Ahmad (16929) and Tabarani in Al-Kabir (19/342) both narrated it through Abu Naeem (who is Fadl bin Dukayn), who said, Abdullah bin Mubashshir, the freedman of Umm Habiba, told us, from Zayd bin Attab, from Muawiya, and he related it. Its chain of transmission is sahih.