Praise be to Allaah.
It is better for a person not to pin his rida’ (upper garment); rather he should wear it over his shoulders. But if he is working, such as a cook or a coffee seller and the like, and he wants to pin it together, there is nothing wrong with it. As for what is referred to in the question about some people fixing it with pins from the neck to the navel, so that it is like a shirt, I doubt that this is permissible, because in that case it resembles a shirt and the Prophet (blessings and peace of Allah be upon him) said concerning the muhrim that he should not wear a shirt. End quote.