Source: Tafsir al-Ahlam al-Kabir (Ibn Sirin)
Yawning in a dream indicates illness or an action for which Satan blames him. It indicates laziness and unemployment.
Source: Ta'tir al-Anam fi Ta'bir al-Manam (Al-Nabulsi)
Yawning indicates worry and grief. Whoever sees himself yawn will fall into hardship.
Source: Al-Isharat fi Ilm al-Ibarat (Ibn Shahin)
Yawning is interpreted as illness. Whoever sees himself covering his mouth when yawning is following the Sunnah.