It is narrated from Sayyiduna Imran bin Husayn (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) led them in prayer and he (peace and blessings be upon him) forgot; then he (peace and blessings be upon him) performed the two prostrations of forgetfulness, then recited the tashahhud and gave the salam.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3896