What should one do who can find neither water nor earth for purification, and is he required to repeat the prayer after one of them becomes available?

If a person is imprisoned or crucified and finds neither water nor earth, he should pray as he is, and his prayer will be complete and he does not need to repeat it. This is based on the Almighty's saying: "So fear Allah as much as you are able," and "Allah does not burden a soul beyond its capacity," and the Prophet's (peace be upon him) saying: "When I command you to do something, do as much of it as you can." Abu Hanifa, Sufyan al-Thawri, and al-Awza'i, however, are of the view that one in such a situation should not pray until he finds water.