As two important Islamic sects, Shia and Sunni, have divisions within themselves, but they have many common points among beliefs and religious issues, and to clarify the difference between Shia and Sunni, it is first necessary to see what these two sects have in common.
A) Commonalities in belief principles
Belief in the existence of God Almighty and His Oneness
Belief in prophethood and mission that God has sent people called messengers and prophets to the people to guide people, and the last of them is Hazrat Muhammad bin Abdullah.
Belief in resurrection and eternal life after death and measuring human actions and reward and punishment in the afterlife
Belief that the Qur'an is a divine book and was revealed by God to the Prophet of Islam Muhammad bin Abdullah (PBUH).
b) Commonalities in legal issues and jurisprudential branches
A- In obligations
prayer
Hajj
fasting
Zakat
Ordering good deeds and forbidding the evil
B- In taboos
a lie
absence
drinking wine
The honor of Ghana
theft
Adultery and...
In many halal and haram issues, although they differ in the details and conditions of all these principles but in main issues Sunni and Shia Muslims are as same as each other.
The main difference between Shia and Sunni is in the issue of the succession of the Holy Prophet Muhammad bin Abdullah (PBUH). For the succession of that Prophet, the Shia considers conditions such as: infallibility, knowledge and full knowledge of the universe, human beings and our upbringing necessary. Therefore, the appointment of a successor is by God, not the choice of the people, because the people are not aware of the existence of these conditions in a person. Unlike the Sunnis who do not consider such conditions necessary and the root of this difference can be seen in the understanding of the meaning of the mission and prophethood:
1- Is the mission and prophethood a valid authority?
2- Or that the mission and prophethood is a real position that only a person who has sensual and inherent perfections can reach such a position, and in other words, the order of the universe requires such a requirement as a necessity, that is, there must be a person who mediates between creation and There is a creator, and the existence of such ranks in the universe is necessary, and this position is a formative and real position, not just a credit and empty of reality, although the acquisition of all these positions is due to divine blessings, because to God we are all in existence and perfection. They need God for their existence.
What separates the Shiite thought from the Sunnis in this matter is this second understanding of the concept of mission and prophethood, therefore, they consider the absolute infallibility and knowledge of the Prophet as a condition for the Messenger and the Prophet, and for the same reason that they consider the existence of the Prophet to be necessary, the continuation of this position They also know that although the position of legislation and revelation regarding the completion of the Sharia and the seal of the Prophet of Islam Muhammad bin Abdullah (PBUH) is not continuous, but his other authorities, who are the external and internal guardianship, the explanation of the Sharia, and the intermediary between God and His people, and divine authority. Being cannot be removed and is continuous. In other words, Sunnis believe that after the death of the Holy Prophet (PBUH), just as the revelation was cut off and there is no connection with God Almighty, in all matters, only what has reached us through the Messenger of God (PBUH) is sufficient. The rest of the issues are based on our own inferences, but Shia believe that even though the revelation has been interrupted, we need an infallible person to explain the divine verses and decrees for us and to express what is the true divine decree. Not what one infers.
For more information, you can refer to the book "Shia in Islam" written by Allameh Tabatabai.
