Sajda Sahuw If I Went To The Stage Of Salam In 2nd Rakah
If, in a four-rak‘ah prayer, a person forgets to sit for the first tashahhud (qa‘dah al-ula) after the second rak‘ah and stands up for the third rak‘ah, then because the first sitting is wajib (necessary), sajdah sahw becomes obligatory due to leaving it out. If the person has already stood up fully straight, they should not sit back down. Rather, they should continue the prayer and perform sajdah sahw before giving salam at the end. If they remember during the prayer, they should complete the prayer and then perform sajdah sahw at the end. If they remember before giving salam and are still in the state of prayer, they will still perform sajdah sahw at the end. And Allah knows best.