Sunan an Nasai
2676
Sahih+2

It was narrated that Ibn 'Umar said; "A man came to the Prophet and said:'What should we wear when we enter Ihram?' He said: 'Do not wear a shirt, or an 'Imamah, or pants, or a burnouts, or Khuffs unless you cannot find any sandals. If you cannot find any sandals, then wear something that comes beneath the ankles

SahihAbu Ghuddah
SahihAl-Albani