Is there any ruling on celebrating sport team wins and dressing up in sport team clothing or colors to show support for a team such as what many people are doing here nowadays for the Blue Jays?
Ash-Shaykh Saalih al-Fawzaan was asked regarding wearing the clothing which have a kaafir sport player’s picture on it or his name on it, so he, may Allah preserve him, replied by saying:
هذا تعظيم للكافر ، مادام يلبس الثوب الذي عليه اسم الكافر أو صورته هذا تعظيم للكافر ، فلا يجوز هذا أقل أحواله أنه محرم ، وإن كان يعظمه يخشى على ردته . نعم .
This is venerating the kaafir , as long as he wears the clothing which has the name of the kaafir on it or his picture on it then it is considered as venerating the kaafir. Thus, this is impermissible, the least (what can be said about it) is (that it is) impermissible, and if he (actually) intends to venerate him then apostasy is feared for him. Na’am
AbdulFattaah bin Uthman