Sahih Bukhari Volume 2, Book 18, Hadith 1093

وَزَادَ اللَّيْثُ قَالَ حَدَّثَنِي يُونُسُ، عَنِ ابْنِ شِهَابٍ، قَالَ سَالِمٌ كَانَ ابْنُ عُمَرَ ـ رضى الله عنهما ـ يَجْمَعُ بَيْنَ الْمَغْرِبِ وَالْعِشَاءِ بِالْمُزْدَلِفَةِ‏.‏ قَالَ سَالِمٌ وَأَخَّرَ ابْنُ عُمَرَ الْمَغْرِبَ، وَكَانَ اسْتُصْرِخَ عَلَى امْرَأَتِهِ صَفِيَّةَ بِنْتِ أَبِي عُبَيْدٍ فَقُلْتُ لَهُ الصَّلاَةُ‏.‏ فَقَالَ سِرْ‏.‏ فَقُلْتُ الصَّلاَةُ‏.‏ فَقَالَ سِرْ‏.‏ حَتَّى سَارَ مِيلَيْنِ أَوْ ثَلاَثَةً ثُمَّ نَزَلَ فَصَلَّى ثُمَّ قَالَ هَكَذَا رَأَيْتُ النَّبِيَّ صلى الله عليه وسلم يُصَلِّي إِذَا أَعْجَلَهُ السَّيْرُ‏.‏ وَقَالَ عَبْدُ اللَّهِ رَأَيْتُ النَّبِيَّ صلى الله عليه وسلم إِذَا أَعْجَلَهُ السَّيْرُ يُؤَخِّرُ الْمَغْرِبَ، فَيُصَلِّيهَا ثَلاَثًا ثُمَّ يُسَلِّمُ، ثُمَّ قَلَّمَا يَلْبَثُ حَتَّى يُقِيمَ الْعِشَاءَ فَيُصَلِّيَهَا رَكْعَتَيْنِ ثُمَّ يُسَلِّمُ، وَلاَ يُسَبِّحُ بَعْدَ الْعِشَاءِ حَتَّى يَقُومَ مِنْ جَوْفِ اللَّيْلِ‏

And Salim added, "Ibn 'Umar used to pray the Maghrib and 'Isha prayers together in Al-Muzdalifa." Salim said, "Ibn 'Umar delayed the Maghrib prayer because at that time he heard the news of the death of his wife Safiya bint Abi 'Ubaid. I said to him, 'The prayer (is due).' He said, 'Go on.' Again I said, 'The prayer (is due).' He said, 'Go on,' till we covered two or three miles. Then he got down, prayed and said, 'I saw the Prophet praying in this way, whenever he was in a hurry during the journey.' 'Abdullah (bin 'Umar) added, "Whenever the Prophet was in a hurry, he used to delay the Maghrib prayer and then offer three Rakat (of the Maghrib) and perform Taslim, and after waiting for a short while, Iqama used to be pronounced for the 'Isha prayer when he would offer two Rakat and perform Taslim. He would never offer any optional prayer till the middle of the night (when he used to pray the Tahajjud)."