It is narrated from Abu Hurairah (may Allah be pleased with him) that after leading two rak‘ahs, the Messenger of Allah (ﷺ) turned back, and Dhu’l-Yadayn (the one with long arms) said to him: “Did you forget, or has the prayer been shortened?” The Prophet (ﷺ) asked the people: “Is Dhu’l-Yadayn speaking the truth?” The people said: “Yes.” Then the Messenger of Allah (ﷺ) stood up and led the remaining two rak‘ahs, then gave salam, then said takbeer ﴿الله اكبر﴾ and performed a prostration as long as or longer than the previous prostrations, then raised his head, then said takbeer and performed another prostration as long as or longer than the previous prostrations, then raised his head.
Hadith Referenceمسند الإمام الشافعي / كتاب الصلاة / 330
Hadith Takhrijأخرجه البخاري: السهو، باب من لم يتشهد في سجدتي السهو: 1228 - ومسلم: المساجد، باب السهو في الصلاة والسجود له: 573.