Sahih al-Bukhari 168
Sahih al-Bukhari · Book 4: Ablutions (Wudu') · While performing ablution or taking a bath one should start from the right side of the body
Narrated `Aisha:
حَدَّثَنَا حَفْصُ بْنُ عُمَرَ ، قَالَ حَدَّثَنَا شُعْبَةُ ، قَالَ أَخْبَرَنِي أَشْعَثُ بْنُ سُلَيْمٍ ، قَالَ سَمِعْتُ أَبِي ، عَنْ مَسْرُوقٍ ، عَنْ عَائِشَةَ ، قَالَتْ كَانَ النَّبِيُّ صلى الله عليه وسلم يُعْجِبُهُ التَّيَمُّنُ فِي تَنَعُّلِهِ وَتَرَجُّلِهِ وَطُهُورِهِ وَفِي شَأْنِهِ كُلِّهِ.
The Prophet (ﷺ) used to like to start from the right side on wearing shoes, combing his hair and cleaning or washing himself and on doing anything else.