The inscription reads:
al-jud min akhlaq ahl al-janna (Generosity is a disposition of the dwellers of Paradise).
This is a line that occurs on a number of dishes and bowls from this period. What is very unusual is the combination of this, written in the very elegant kufic seen here, with the coloured band around the rim. The colouring and drawing of that are more typical of vessels found at Samarkand and make a Nishapur provenance much less probable.