Jaf'ar b. Musafir said in his version: (He prayed) the two rak'ahs sitting between the two adhans. He added the word "sitting".
In-book : Book 5, Hadith 112
English translation : Book 5, Hadith 1356
5. Prayer (Kitab Al-Salat): Voluntary Prayers
باب فِي صَلاَةِ اللَّيْلِ