Al-Nabulsi said: Yawning in a dream is a sign of committing sin and of deeds that please Satan, such as crying out and weeping and abandoning the prayer out of laziness. A person seeing himself in a state of yawning sometimes signifies prevailing over the enemy, doing deeds of reward, and good.
Seeing oneself yawn a great deal is a sign of heedlessness and laziness. Again, the state of yawning signifies that the dreamer will catch an illness that will find no cure. If a person sees himself put his hand to his mouth while yawning, saying "Praise be to Allah," it signifies that he is upon the truth and on the path of the Truth.