Is it permissible for two friends to agree, as a form of encouragement for studying and competition, that whoever fails to study a certain part will buy a simple item (worth 5 or 10 riyals) for the other who did study, as a punishment for the one who fell short?

Agreeing to pay a sum of money to someone who has not performed a specific task is a forbidden form of maysir (gambling), and the Messenger of Allah (peace and blessings of Allah be upon him) prohibited it, except in matters that aid jihad in the way of Allah, such as horse races, camel races, or archery. Quran, Hadith, and Fiqh competitions are assimilated to this. A fatwa from the Permanent Committee for Issuing Fatwas states that betting on the results of matches or other events is impermissible, due to it involving gambling and consuming wealth unjustly.