Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) narrates about the Noble Prophet (peace and blessings be upon him): He led five rak'ahs in the Zuhr prayer. It was submitted to him: Has something been added to the prayer? The Noble Prophet (peace and blessings be upon him) inquired: What has happened? They said: You have led five rak'ahs. So the Noble Prophet (peace and blessings be upon him) performed two prostrations of forgetfulness after concluding the prayer with salam.
Hadith Referenceصحیح ابن حبان / كتاب الصلاة / 2658
Hadith Gradingفضيلة الشيخ الإمام محمد ناصر الدين الألبانيصحيح - «صحيح أبي داود» (934): ق.فضيلة الشيخ العلّامة شُعيب الأرناؤوطإسناده صحيح على شرط الشيخين