كتاب الفضائل
43
The Book of Virtues
(20)
Chapter: His Avoidance Of Sin, His Choosing The Easier Of Permissible Things, And His Vengeance For The Sake Of Allah If His Sacred Limits Were Transgressed
(20)
باب مُبَاعَدَتِهِ صلى الله عليه وسلم لِلآثَامِ وَاخْتِيَارِهِ مِنَ الْمُبَاحِ أَسْهَلَهُ وَانْتِقَامِهِ ل

'A'isha reported:

Never did Allah's Messenger (ﷺ) make a choice between two things but adopting the easier one as compared to the difficult one, but his choice for the easier one was only in case it did not involve any sin, but if it involved sin he was the one who was the farthest from it amongst the people.
حَدَّثَنَا أَبُو كُرَيْبٍ، حَدَّثَنَا أَبُو أُسَامَةَ، عَنْ هِشَامٍ، عَنْ أَبِيهِ، عَنْ عَائِشَةَ، قَالَتْ مَا خُيِّرَ رَسُولُ اللَّهِ صلى الله عليه وسلم بَيْنَ أَمْرَيْنِ أَحَدُهُمَا أَيْسَرُ مِنَ الآخَرِ إِلاَّ اخْتَارَ أَيْسَرَهُمَا مَا لَمْ يَكُنْ إِثْمًا فَإِنْ كَانَ إِثْمًا كَانَ أَبْعَدَ النَّاسِ مِنْهُ ‏.‏
Reference : Sahih Muslim 2327 d
In-book reference : Book 43, Hadith 106
USC-MSA web (English) reference : Book 30, Hadith 5754
  (deprecated numbering scheme)