e7.0 The things that nullify one's ablution
CONTACT OF MAN AND WOMAN'S SKIN
e7.3 The third cause of minor ritual impurity is when any, no matter how little, of the two skins of a man and woman touch (N: husband and wife, for example) when they are not each other's not marriageable kin (Ar. mahram, def:m6), even if they touch without sexual desire, or unintentionally, and even if with tongue or a nonfunctional or surplus limb; though touching does not include contact with teeth, nails, hair, or a severed limb.
Ablution is also nullified by touching AN AGED person or a corpse (N: of the opposite sex) but not by touching a member of one's not marriageable kin, or a child who is younger than the age that usually evokes sexual interest.
One's ablution is not nullified when one is uncertain about:
(1) whether one touched a male or female;
(2) whether one touched hair or skin;
(3) or whether the person one touched was one's not marriageable kin or not.