Shaikh Ibn ‘Uthaymeen - may Allaah have mercy on him - said:
"It is not from the Sunnah to say a’uuthobillaahi mina ash-Shaytaani rajeem (I seek refuge in Allah from the Devil the outcast) when one yawns, because the Prophet Muhammad (Salla’Allaahu Alayhi wa Salam) - never used to do this nor did he command others to do it.
And as for the verse;
'And if an evil suggestion comes to you from Satan, then seek refuge in Allah . Indeed, He is Hearing and Knowing.'
[Surah al-‘Araafxx: Ayahx 200]
This ‘evil suggestion’ mentioned in this verse refers to sin or leaving off a commandment of Allah.
Similarly, saying alhamdulilaah (all praise is for Allah) when burping, was never commanded by the Prophet Muhammad (Salla’Allaahu Alayhi wa Salam) - nor did he himself ever say it when burping.”
[Liqaa al-Baab al-Maftooh 89]