Praise be to Allah.
It is not permissible to change the Arabic numerals which are currently in use and replace them with the numerals used in the western world, for the following reasons:
Firstly: there is no proof of what the advocates of change say about the numerals used in the West being Arabic numerals. What is known is something other than that, as is proven by reality and the fact that for centuries the current numerals were used in different circumstances and different fields, which makes them Arabic. There are words in the Arabic language which were not originally Arabic, but they became part of the Arabic language through usage, to the extent that some of these words are to be found in the Qur’aan; these words are described as Arabized.
Secondly: this idea has bad consequences and harmful effects, because it is a step towards the gradual Westernization of Islamic societies.
Thirdly: it paves the way for changing the Arabic script and using Latin script instead of Arabic, even in the long run.
Fourthly: it is an aspect of imitating the West and approving of its ways.
Fifthly: all the copies of the Qur’aan (masaahif), books of Tafseer, Arabic dictionaries and other books use the current Arabic numerals in numbering their pages etc., and in referring to other sources. All these books represent a vast store of knowledge. If the foreign numerals are used instead, this will make it very difficult for the coming generation to access this vast store of knowledge.
Sixthly: It is not necessary to follow certain Arab countries which are accustomed to using these European numerals. Many of these countries have also abolished something even more important, which is ruling according to the whole sharee’ah of Allaah, which is the source of honour, power and happiness in this world and the next, so what they (those countries) have done is nothing to go by.