Yazid bin Zari' يزيد بن زريع · The Book of Forgetfulness (In Prayer)

"The Messenger of Allah (ﷺ) was ill, and we prayed behind him while he was sitting, and Abu Bakr repeated his takbirs so that the people could hear them. He turned to us and saw us standing, so he gestured to us to sit down. So we prayed behind him sitting. When he said the salam he said: 'Just now you were doing what the Persians and Romans do for their kings when they are sitting. Do not do that.…

"The Messenger of Allah (ﷺ) led us in praying two rak'ahs, then he stood up and did not sit, and the people stood up with him. When he finished the prayer, and we were waiting for him to say the taslim, he said the takbir and prostrated twice while sitting, before the taslim. Then he said the taslim."

The Prophet (ﷺ) prostrated after the salam when he was not sure.