Temporary amnesia during exams, anyone? A duʿā` to prevent that:

نسأل الله أن ينفعنا بما قرأنا و يرده إلينا عند الحاجة

Translation: We ask Allāh to make what we have read beneficial for us and to return it to us in times of necessity.

Transliteration: Nas`al Allāh an yanfaʿanā bemā qara`nā wa yarudhu ilayna ʿind al-ḥājah.

A naḥow professor of mine often makes this duʿā` at the end of each class.

NOTE: This is not a duʿā` from the Qur`ān or Sunnah, it is simply a well worded and much needed duʿā`.