The inscription has been translated:
In the name of God, the Compassionate, the Merciful. May God's absolute blessing be upon the Prophet Muhammad, and his family, and salute him with all respects. Say: It is a message of importance (Qur'an, sura xxxviii, v.67). This is the tomb of 'Umar b. 'Umran al-Fawqi, known as ..... al-Baytar (the veterinerary surgeon or horse doctor). He died on the 12th of the month of shawwal, the year 574, and he confesses that there is no god but The God, He Alone, no partner has He, and Muhammad is His servant and His messenger.
The so-called pillar tombstones, rare in Egypt, are commonly found in North Africa and more particularly in Tunisia where they range in date between the eleventh and twelfth centuries. This example belongs to this group of which the rather coarse-grained marble and the relief carved foliate kufic are characteristic. Two similar examples were sold in these Rooms 12 October 1999, lots 326 and 327. For further discussion, please see Zbiss, M. Z.: Inscriptions de Monastir, Tunis, 1960.