Ruling on wearing graduation hat
27-6-2016 | IslamWeb
Question:
Is wearing a graduation hat forbidden in Islam?
Answer:
All perfect praise be to Allaah, The Lord of the worlds. I testify that there is none worthy of worship except Allaah and that Muhammad 
is His slave and Messenger.
In principle, all types of clothes are permissible unless there is textual evidence that they are forbidden; this is according to the general Islamic rule, “In principle, all things are permissible.” Allaah Almighty says (what means): {It is He Who created for you all of that which is on the earth.} [Quran 2:29]
This ruling includes the graduation hat.
An item of clothing is not forbidden unless wearing it leads to a violation of Islamic law, such as imitating the non-Muslims in the way they dress, which is prohibited for both men and women. This is also the case if it does not cover the woman's body.
It should be noted though that only the clothes that are peculiar to the non-Muslims are subject to this ruling, and not clothes that are common between Muslims and non-Muslims. Ibn Hajar 
said in al-Fat-h, “If we say that forbidding wearing them (red saddle-cloths of non-Arabs made of Deebaj and silk) is because of imitating the non-Arabs, then this is for a religious benefit. But if wearing them used to be peculiar to their rituals at that time but now it is not peculiar to their rituals, then that meaning no longer exists, and, hence, they are no longer disliked.”
Allaah knows best.