In a dream it is immorality and deeds that please Satan, such as wailing and laziness about prayer. Yawning [tatha'ub] in a dream indicates springing [wuthub] upon opponents, and reward [thawab], because a person is commanded to suppress it when in prayer, as a guard against Satan. It may indicate the exposure of a person's condition. It may be an illness from which its owner does not recover.
Dream meaning · al-Nabulsi
Yawning تثاؤب
Source: al-Nabulsi, Ta'tir al-Anam fi Ta'bir al-Manam, p. 46. English translation by iDreamBot. Quran verses: Quran.com, Saheeh International.