Abu Hurairah reported,

The Messenger of Allah ﷺ led either the Dhuhr or the Asr prayer, and he gave the closing salutation after two units and turned away.Dhul-Shamalayn Ibn Amr said to him, "Has the prayer been shortened, or did you forget?"The Prophet ﷺ asked, "What is Dhul-Yadayn saying?"The people replied, "He is right, Prophet of Allah."So he completed with them the two units he had omitted.Ibn Shihab said, Saeed bin Musayab reported this account to me from Abu Hurairah. He added, and Abu Salama bin Abdul-Rahman, Abu Bakr bin Abdul-Rahman bin Harith, and Ubaydullah bin Abdullah also reported it to me.

Nasai 1232

Sahih

أخبرنا أبو داود قال حدثنا يعقوب قال حدثنا أبي عن صالح عن ابن شهاب أن أبا بكر بن سليمان بن أبي حثمة أخبره أنه بلغه أن رسول الله ﷺ صلى ركعتين فقال له ذو الشمالين نحوه قال ابن شهاب أخبرني هذا الخبر سعيد بن المسيب عن أبي هريرة قال وأخبرنيه أبو سلمة بن عبد الرحمن وأبو بكر بن عبد الرحمن بن الحارث وعبيد الله بن عبد الله

النسائي 1232صحيح
Contents
Reference
Commentary
Ayat
Collection
Sunan Nasai Sughra
Book
Forgetfulness
Chapter
What one should do if he gives salaam after two rakahs forgetfully and speaks
Numbering
Darussalam 1232
Nasai 1232