Ibn 'Abbas reported:

The Messenger of Allah (ﷺ) observed the noon and afternoon prayers together in Medina without being in a state of fear or in a state of journey. (Abu Zubair said: I asked Sa'id [one of the narrators] why he did that. He said: I asked Ibn 'Abbas as you have asked me, and he replied that he [the Holy Prophet] wanted that no one among his Ummah should be put to [unnecessary] hardship.)
وَحَدَّثَنَا أَحْمَدُ بْنُ يُونُسَ، وَعَوْنُ بْنُ سَلاَّمٍ، جَمِيعًا عَنْ زُهَيْرٍ، - قَالَ ابْنُ يُونُسَ حَدَّثَنَا زُهَيْرٌ، - حَدَّثَنَا أَبُو الزُّبَيْرِ، عَنْ سَعِيدِ بْنِ جُبَيْرٍ، عَنِ ابْنِ عَبَّاسٍ، قَالَ صَلَّى رَسُولُ اللَّهِ صلى الله عليه وسلم الظُّهْرَ وَالْعَصْرَ جَمِيعًا بِالْمَدِينَةِ فِي غَيْرِ خَوْفٍ وَلاَ سَفَرٍ ‏.‏ قَالَ أَبُو الزُّبَيْرِ فَسَأَلْتُ سَعِيدًا لِمَ فَعَلَ ذَلِكَ فَقَالَ سَأَلْتُ ابْنَ عَبَّاسٍ كَمَا سَأَلْتَنِي فَقَالَ أَرَادَ أَنْ لاَ يُحْرِجَ أَحَدًا مِنْ أُمَّتِهِ ‏.‏
Reference : Sahih Muslim 705 b
In-book reference : Book 6, Hadith 60
USC-MSA web (English) reference : Book 4, Hadith 1516
  (deprecated numbering scheme)