What are the details and differences in the jurists' independent reasoning (ijtihad) regarding the pillars (arkan) and obligations (wajibat) of prayer, and what are their proofs for that?

Scholars have divided the actions of prayer into obligations (wājibāt) and Sunnahs, while Hanbali jurists have divided them into pillars (arkān), obligations (wājibāt), and Sunnahs.

According to them, the pillars are those actions that cannot be omitted intentionally or by forgetfulness. Obligations, however, can be dropped due to forgetfulness or ignorance and are compensated for by the prostration of forgetfulness (sujūd al-sahw).

The Hanafis differentiate between fard (or rukn), which is established by definitive proof, and wajib, the omission of which intentionally does not invalidate the prayer, but its performer is considered blameworthy. If omitted by forgetfulness, one performs the prostration of forgetfulness.

The Malikis and Shafi’is divide the actions of prayer into obligations (wājibāt) and Sunnahs.

The majority of scholars base the obligatoriness of pillars and obligations on the hadith of the one who prayed incorrectly. They adduce other proofs for the obligatoriness of actions not mentioned in that hadith, such as intention (niyyah), the final tashahhud, and the salutation (taslīm).

The disagreement regarding whether intention is a condition (shart) or a pillar (rukn) is a terminological dispute, with agreement on its necessity.