Alqamah once led the people in prayer and prayed five rak'ahs. When he gave the salam, the people said: You have led five rak'ahs. Alqamah said: Do you also say so, O A'war - addressing Ibrahim (al-Nakha'i)? He said: Yes. So Alqamah performed the two prostrations of forgetfulness (sahw), then recited the tashahhud and gave the salam, then turned to the people and related to them the narration of Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) had done the same.
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 9807