What should one do if the urge to relieve oneself strikes during the prayer?

The questioner : If these excuses arise during the prayer, is it permissible for him to separate from the congregation? For example, if the urge to relieve oneself strikes him during the prayer, is it permissible for him to separate?

The Shaykh : Yes, he may separate, unless he would gain no benefit from doing so, meaning that the imam shortens the prayer to the extent of the obligatory. In this case, would he gain anything by separating? Because if the imam shortens it, the imam is like him, and he would gain nothing by separating. Now, is it permissible for him to break off the prayer? Yes, he may break off the prayer; he may break it off if this excuse occurs, because he cannot complete it in the manner required of him, unless he would gain no benefit from breaking it off, in which case he does not break it off.