ANSWER:

This is not sinful, but the sunnah is to suppress it as much as you can and to cover your mouth inside and outside prayers while yawning.

With regards to yawning, since it comes from Satan, is it a sin to do? Sometimes I’m not able to control it. Also, do we have to cover our mouths if we do it OUTSIDE of prayer? And does it matter if we use our hands, or our fists to cover our mouths? Thank you for your time!