When we say religion is one, does it mean aqeedah is same and Shari’ah is different for different prophets?

When we say religion is one, it means the fundamental aspects of the religion, the usul ud deen, they are one, while the rest of the details are different. This does not necessarily mean that the entire aqeedah is the same including the details and it does not necessarily mean the entire law is different.

As far as the aqeedah there can be no abrogation in it; meaning if a previous prophet was told that this is something we were asked to believe in it then that cannot be changed. However, when we say the things of the aqeedah if change could happen then it is not the beliefs but the actions related to the aqeedah e.g. certain laws have been legislated in Islam which in the aim of barring people from approaching shirk. These laws are very detailed and strict and might not have been present in previous religions. Everything which could be a doorway or path to shirk, the Prophet (may Allah’s peace and blessings be on him) forbade it even if that thing was not shirk itself so that it would not lead to shirk. These aren’t beliefs, these are rulings related to the aqeedah. As far as the fundamental aspects, the belief in Allah, the prophet, the angels, books etc and even salah and fasting and prohibition of satan, types of sins, were the same in previous religions. Even the prohibition   of eating pork or drinking wine etc was present in previous religions. Dr Bilal Philips in his book, The True Message of Jesus Christ,[1] has very nicely documented and established that Christianity and Judaism, according to their original form had salah and zakat or compulsory charity. Several prohibitions, such as dress code etc that are now only associated with Islam were present in the previous religions. These religions have been so distorted or their laws have been covered up that’s why people now associate these things only with Islam.[2]

References:

[1] P 63-69

[2] U Aziz us-Samad, Islam and Christianity, p 3-11