From Sahih Bukhari (Hadith 4133):
Narrated `Abdullah bin `Umar:Allah's Messenger (ﷺ) led the Fear-prayer with one of the two batches of the army while the other (batch) faced the enemy. Then the first batch went away and took places of their companions (i.e. second batch) and the second batch came and he led his second rak`a with them. Then he (i.e. the Prophet: finished his prayer with Taslim and then each of the two batches got up and completed their remaining one rak`a)
Reference: Bukhari 4133