It wasnarrated from 'Alqamah that Ibn Mas'ud prostrated twice fortheprostrations of forgetfulness after the Salam, and he mentionedthatthe Prophet (ﷺ) did that." (RU)
English reference (RU): Vol. 1, Book 5, Hadith 1218 (RU)
Arabic reference (RU): Book 5, Hadith 1275 (RU)