Sahih al-Bukhari 1109
Shortening the Prayers (At-Taqseer)
Should the Adhan and Iqama be pronounced when the Maghrib and Isha prayers are offered together
Narrated Az-Zuhri: Salim told me, "`Abdullah bin `Umar said, 'I saw Allah's Messenger (ﷺ) delaying the Maghrib prayer till he offered it along with the `Isha prayer whenever he was in a hurry during the journey.' " Salim said, "Abdullah bin `Umar used to do the same whenever he was in a hurry during the journey. After making the call for Iqama, for the Maghrib prayer he used to offer three rak`at and then perform Taslim. After waiting for a short while, he would pronounce the Iqama for the `Isha' prayer and offer two rak`at and perform Taslim. He never prayed any Nawafil in between the two prayers or after the `Isha' prayers till he got up in the middle of the night (for Tahajjud prayer)."