Musannaf Ibn Abi Shayba 13:98

Jarir narrated to us, from Mughira, from Hammad, from Ibrahim, who said: There is no harm in the tailor taking a fee for a known wage, or taking it without that, provided he marks it with something, or cuts it, or gives him thread and needles, or sews something into it. But if he does not mark it with this or with any part of it, then he must not take any surplus.