بُلُوغُ الْمَرَامِ
Bulugh al-Maram 339
The Book of Prayer
وَعَنْ ثَوْبَانَ - رضى الله عنه - أَنَّ اَلنَّبِيَّ - صلى الله عليه وسلم -قَالَ : { لِكُلِّ سَهْوٍ سَجْدَتَانِ بَعْدَمَا يُسَلِّمُ } رَوَاهُ أَبُو دَاوُدَ , وَابْنُ مَاجَهْ بِسَنَدٍ ضَعِيفٍ . [1]
Narrated Thawban (RA): The Prophet (ﷺ) said: "There are two prostrations after the Taslim (salutation) for each forgetfulness." [Abu Dawud and Ibn Majah reported it through a weak chain of narrators].
Sunnah.com reference: Book 2, Hadith 240