I believe this is the question that a user was trying to get at here. Geas states that you cast the spell on a creature, thereby
forcing it to carry out some service or refrain from some action or course of activity as you decide.
The use of the word "forcing" would seem to imply the creature has no choice but to carry out the action you demand of it. However, the spell further describes
While the creature is charmed by you, it takes 5d10 psychic damage each time it acts in a manner directly counter to your instructions, but no more than once each day.
This makes no sense unless it is possible for the creature to disobey you. If the creature has the option to disobey you, then the word "forced" is inaccurate. Should we therefore dismiss the first sentence of this spell as (inaccurate) fluff? Can we safely assume that the creature is not forced at all, but rather coerced into service by the threat of 5d10 psychic damage (which may be an empty threat against creatures with sufficient hit points)?