The Messenger of Allah ﷺ led them in prayer and made a mistake. After he gave the closing salutation, he performed two prostrations and then gave the salutation again.
حدثنا وكيع قال حدثني مالك بن أنس عن داود بن الحصين عن أبي سفيان مولى أبي أحمد
أن رسول الله ﷺ صلى بهم فسها فلما سلم سجد سجدتين ثم سلم
Its isnad is sahih. Abu Sufyan is the freed slave of Ibn Abu Ahmad, so "Ibn" was dropped from the printed edition, and his name is Abdullah bin Abu Ahmad bin Jahsh. Tirmidhi related it, 2/240, no. 395, in the Book of Prayer, chapter on what has been said regarding the tashahhud in the two prostrations of forgetfulness, and he said, hasan sahih. Nasai also related it, 3/26, no. 1236, in the Book of Forgetfulness.