Yahya related to me from Malik, from Nafi, that Abdullah ibn Umarused to say, "Someone in ihram should not be cupped, except when thereis no other alternative."Malik said, "Someone who is inihram should not be cupped except when it is necessary."
USC-MSA web (English) reference: Book 20, Hadith 76
Arabic reference: Book 20, Hadith 780