Maliks Muwatta Book 21, Hadith Number 16A.

Section : Things on Which the Tax of One Fifth (Khumus) is Not Obligatory.

Malik said about enemy soldiers who were found on the seashore of a Muslim land, and they claimed that they were merchants and that the sea had driven them ashore, while the Muslims were not able to verify any of that except that their ships were damaged, or they were thirsty and had disembarked without the permission of the Muslims, “I think that it is up to the imam to give his opinion about them, and I do not think that the tax of one fifth is taken from them.”