Is it permissible to combine the Dhuhr and Asr prayers, as well as the Maghrib and Isha prayers, when not traveling, such as when preoccupied with studying during a lecture?

If there is a need to combine two prayers due to continuous work that is difficult to interrupt, or an urgent matter that would be missed by not praying and would lead to the loss of a legitimate interest, there is no harm in combining them, provided that it is not a continuous habit. This is based on the hadith (definition) of Ibn Abbas that the Prophet (peace be upon him) combined Dhuhr and Asr, and Maghrib and Isha, without fear or travel. However, making it a habit is not permissible, as it contradicts the Prophet's actions and his urging to perform prayers at their prescribed times. Some scholars have stated that Ibn Abbas's combining was a "pictorial" combining, meaning performing one prayer at the very end of its time and the other at the very beginning of its time.

If lecture times consistently conflict with prayer times, you should change the course time or the instructor if possible. If not possible, then seek permission and pray in the nearest available place. If you are compelled to remain in the hall, such as during an exam or work that cannot be interrupted, then it is permissible for you to combine Dhuhr and Asr, and Maghrib and Isha. However, it is not permissible to combine Asr with Maghrib because they do not share a common time.