Assalamu aleikum,

Is it permissable to pray in a mosque containing a grave? For example this mosque:

El-Mursi Abul-Abbas Mosque (Arabic: جامع المرسي أبو العباس‎) is a famous mosque in Alexandria, Egypt. It is dedicated to the 13th century Alexandrine Sufi saint el-Mursi Abul Abbas whose tomb it contains.