। ॥ ३१ ॥
In plain words
But where dispassion and the longing for freedom are weak, all the calm and discipline you display is like water shimmering in a desert — a mirage, nothing you could ever actually drink.
Close to the Sanskrit
Where there is weakness of these two — dispassion and desire for liberation — there the qualities beginning with calmness are like water in a desert [mirage]: mere appearance.