How should the intention for the prostration of forgetfulness (sujood as-sahw) be, and does it differ in certain situations, such as forgetting a prostration or the first tashahhud?

If a worshipper performs the taslim (salutation to end the prayer) and then remembers having forgotten a prostration (sujud), and the interval (fasl) has not been long, then he is still considered to be in prayer and does not need a new takbirat al-ihram (opening takbir), but rather builds upon his prayer. If the interval has been long, then he must repeat the entire prayer. The determination of whether the interval is long or short is based on custom and common practice.

If the prayer is not invalidated due to a short interval, the worshipper stands up and performs a complete rak'ah (even if the forgotten prostration was from the last rak'ah), then recites the tashahhud and performs the taslim, and then performs the two prostrations of forgetfulness (sujud al-sahw). Some scholars are of the opinion that if the forgotten prostration was from the last rak'ah, he only performs that prostration, then recites the tashahhud and performs the taslim, and then performs the prostrations of forgetfulness after the taslim.

As for forgetting the first tashahhud, if the worshipper remembers it before standing up completely, he must return and perform the tashahhud, and perform the prostrations of forgetfulness at the end of the prayer. However, if he has stood up completely, his return is disliked. And if he has begun reciting (the Qur'an), his return is forbidden, and he must perform the prostrations of forgetfulness in all cases. If he remembers before rising, there is no sujud al-sahw upon him.

The worshipper must perform the prostrations of forgetfulness with the intention of prostrating for the mistake that occurred, without obsessive thoughts about the type of mistake.