The World Federation One Stop Fiqh

Ruling 651

If a person has water that is only sufficient for performing wuḍūʾ or ghusl with, and he knows that were he to spill the water he would not be able to find any more, in the event that the time for prayers has set in, it is unlawful for him to spill the water; and the obligatory precaution is that he must not spill it even before the time for prayers has set in.