It wasnarrated that Mughirah bin Shu'bah said:
"The Messenger ofAllah(ﷺ) said: 'If anyone of you stands after two Rak'ah, if he hasnot yet stood up fully, let him sit down again, but if he has stoodupfully, then let him not sit down, and let him perform twoprostrationsfor forgetfulness (Sahw).'" (ID)
English reference (ID): Vol. 1, Book 5, Hadith 1208 (ID)
Arabic reference (ID): Book 5, Hadith 1265 (ID)