If a worshiper forgets a rak'ah in Dhuhr prayer and remembers it while sitting for the tashahhud, should he perform the prostration of forgetfulness (sujud al-sahw) before making up the missed rak'ah, or should he pray the rak'ah, then prostrate for forgetfulness, and then say the tasleem?

Whoever forgets a raka'ah and remembers it during the Tashahhud must stand up to complete the missing raka'ah, then perform the Tashahhud, then perform the prostration of forgetfulness (sujud al-sahw), and then give the salutations of peace (taslim). It is not permissible for someone who knows they have a missing raka'ah to give the salutations of peace before completing the prayer, because the prostration of forgetfulness does not compensate for a deficiency in the pillars (arkaan) of the prayer.