Asallam Alykum Warahmatullahi Wabarakatuh
The following is a summary translation taken from the website of Sheikh Uthaymeen Rahimahumullaah ,
http://www.ibnothaimeen.com/all/noor/article_8666.shtml
Seeking refuge after Yawning by Sheikh Uthaymeen Rahimahumullaah
Question: May Allaah give you good, some people say after yawning “I seek refuge in Allaah from the accursed“[Shaytaan (Satan)].” Is this mentioned anywhere?
Answer: This is not mentioned, meaning it is not found (in the Quran or Sunna) that the person should say upon yawning, I seek refuge in Allaah from the accursed“[Shaytaan (Satan)].
Rather it is only mentioned that the person should repress the yawn as much as he is able and if he is not able then he should place his hand over his mouth. And the Prophet(sall-Allaahu ‘alayhi wa sallam)and his family, directed us towards this action at the time of yawning and he didn’t say, “And also seek refuge with Allaah from the accursed “[Shaytaan (Satan)].
” So if someone says, “Did Allaah not say, {And if an evil whisper comes to you from Satan then seek refuge with Allaah . Verily, He is All-Hearer, All-Knower.}(Chapter 7 verse 20) And the Prophet peace and blessings be upon him and his family, has informed us that yawning is from “[Shaytaan (Satan)].
So the answer is, all of this is correct; Allaah says this, {meaning the above verse) and the Prophet peace and blessings be upon him informed us that yawning is from “[Shaytaan (Satan)] But, what is intended by }“an evil whisper” in this noble verse is to preoccupy the person with evil. Either by leaving off something, which is obligatory, or by doing something prohibited. So if the person feels that he is being stressed with this then he should say, “I seek refuge with Allaah from the accused “[Shaytaan (Satan)] As for yawning then the Prophet (sall-Allaahu ‘alayhi wa sallam) has taught us what is legislated to do at the time of yawning.
Allaah Knows Best
Wa Salaam alykum.