Abdullah bin Masud reported,

The Messenger of Allah ﷺ led us in prayer, and I do not know whether he added or omitted something. Ibrahim is the one who said, "I do not know," while Alqama said, "He added or omitted," or it was Abdullah who said this.Then he turned toward us, and we informed him of what he had done. So he folded his leg, faced the qiblah, and performed two prostrations. Then he turned his face toward us and said, "Had anything new occurred in the prayer, I would have told you about it. But I am only a human being. I forget just as you forget. So if I forget, remind me. And whichever of you is uncertain about his prayer, let him seek out what is closest to correctness, complete the prayer on that basis, give the salam, and then perform two prostrations."

Ahmad 4174

Sahih

حدثنا محمد بن جعفر حدثنا شعبة قال كتب إلي منصور وقرأته عليه قال حدثني إبراهيم عن علقمة

عن عبد الله

قال صلى رسول الله ﷺ صلاة لا أدري زاد أم نقص إبراهيم القائل لا يدري علقمة قال زاد أو نقص أو عبد الله ثم استقبلنا فحدثناه بصنيعه فثنى رجله واستقبل القبلة وسجد سجدتين ثم أقبل علينا بوجهه فقال لو حدث في الصلاة شيء لأنبأتكموه ولكن إنما أنا بشر أنسى كما تنسون فإن نسيت فذكروني وأيكم ما شك في صلاته فليتحر أقرب ذلك للصواب فليتم عليه ويسلم ثم يسجد سجدتين

أحمد 4174صحيح
Contents
Reference
Commentary
Ayat
Collection
Musnad Ahmad
Book
Abdullah bin Masud
Numbering
Darussalam 4174
Ahmad 4174