It is narrated from Hazrat Abu Huraira (may Allah be pleased with him) that the Noble Prophet (peace and blessings be upon him) said: Yawning is from the effect of Satan, so when one of you feels like yawning, he should try to restrain it as much as possible.
Hadith Referenceمسند احمد / مسند المكثرين من الصحابة / 10695