Prayer: The Elemental Components of Prayer (Rukn)
Practical Laws of Islam as per the teachings of Ayatullah Sistani
Ruling 928
Some of the obligatory components of the prayer are elemental (rukn), i.e. if one does not perform them – whether intentionally or mistakenly – the prayer is invalid. Some other obligatory components are not elemental, i.e. if they are omitted mistakenly, the prayer is not invalid. There are five rukns of the prayer:
1. Intention;
2. Takbīrat al‑iḥrām while standing;
3. Standing that is joined to rukūʿ, i.e. standing before rukūʿ;
4. Rukūʿ;
5. Two sajdahs in one rakʿah.
If a rukn is intentionally performed more than the prescribed number of times, the prayer is invalid. If it is done mistakenly, and if the additional act is a rukūʿ or two sajdahs in one rakʿah, then based on obligatory precaution, the prayer is invalid; otherwise [i.e. if the additional act is not a rukūʿ or two sajdahs in one rakʿah], it is not invalid.