Sahih Muslim
The Book Pertaining to Clothes and Decoration (Kitab Al-Libas wal-Zinah)
Book Number: 024 / Hadith Number: 5231
Abu Huraire reported Allah's Messenger (may peace be upon him) as saying: When one of you puts on sandals, he should first put in the right foot, and when he takes off he should take off the left one first, or he should put them on together or take them off together.