Is there a Hadith which states that Shaytan enter the mouth when a person yawns?
Yes. Imam Muslim (rahimahullah) has recorded the following Hadith in his Sahih:
Sayyiduna Abu Sa’id Al Khudri (radiyallahu ‘anhu) reports that Rasulullah (sallallahu ‘alayhi wa sallam) said: “When one of you yawns, he should place his hand on his mouth, for Shaytan enters.”
(Sahih Muslim, Hadith: 2995)
And Allah Ta’ala Knows best.
Answered by: Moulana Suhail Motala
Approved by: Moulana Muhammad Abasoomar