The Book of Prayer - Travellers
وَحَدَّثَنَاهُ أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، حَدَّثَنَا أَبُو أُسَامَةَ، حَدَّثَنَا عُبَيْدُ اللَّهِ، عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ، أَنَّهُ نَادَى بِالصَّلاَةِ بِضَجْنَانَ ثُمَّ ذَكَرَ بِمِثْلِهِ وَقَالَ أَلاَ صَلُّوا فِي رِحَالِكُمْ . وَلَمْ يُعِدْ ثَانِيَةً أَلاَ صَلُّوا فِي الرِّحَالِ . مِنْ قَوْلِ ابْنِ عُمَرَ .Ibn 'Umar reported that he summoned (people) to prayer at a place (known as) Dajnan, and the rest of the hadith is the same, and then said:Pray in your dwellings, but he did not repeat for the second time words of Ibn 'Umar (Pray in your dwellings)
From Sahih Muslim, whose reports the scholars accept as authentic.