Narrated `Abdullah bin Malik bin Buhaina: Whenever the Prophet used to offer prayer he used to keep arms away (from the body) so that the whiteness of his armpits was visible.
Hadith ReferenceSahih Bukhari / The Book of Adhan (Sufa-tus-Salat) / Hadith: 807
Hadith Gradingمحدثین:أحاديث صحيح البخاريّ كلّها صحيحة