Sunan an-Nasa'i Book 48, Hadith 58
"The Messenger of Allah said: 'May Allah curse the woman who affixes hair extensions and the woman who has that done.'"
The Messenger of Allah cursed the woman who affixes hair extensions and the woman who has that done, the woman who does tattoos and the woman who has that done.
A woman came to 'Abdullah bin Mas'ud and said: "I am a woman with little hair, is it alright for me to add extensions to my hair?" He said: "No." She said: "Is it something that you heard from the Messenger of Allah and I find it in the Book of Allah." And he quoted the Hadith.