Ata ibn Yasar عطاء بن يسار أبو محمد مولى ميمونة · The Book of Forgetfulness (In Prayer)

Abu Hurairah said: "The Messenger of Allah (ﷺ) stood up to pray and we stood up with him. A Bedouin said- while he was praying- 'O Allah, have mercy on me and Muhammad and do not have mercy on anyone else.' When the Messenger of Allah (ﷺ) said the Salam, he said to the Bedouin: 'You have limited something vast," meaning the mercy of Allah (SWT)."

The Prophet (ﷺ) led them in prayer and forgot (how many rak'ahs he had prayed), then he prostrated twice, then he said the salam.

"The Messenger of Allah (ﷺ) said the salam after three rak'ahs of 'Asr, then he entered his house. A man called Al-Khibaq stood up and said: 'Has the prayer been shortened, O Messenger of Allah?' He came out angry, dragging his upper garment and said: 'Is he speaking the truth?' They said: 'Yes.' So he stood and prayed that rak'ah, then he said the salam, then prostrated twice, then he said the salam (again)."