Religious primes were found to activate cleanliness concepts in a word-stem completion task (Study 1), and increased the subjective value of cleaning products (Study 2). In a final study, cleaning primes increased ratings of religious value. These studies suggest a mutual association between religiousness and cleanliness, and that each may activate the other as goals for personal purity.
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Recently there has been renewed interest in the psychological literature in disgust as moral emotion. Rozin, Haidt, and McCauley (2000) distinguish between core disgust, elicited by rotting food or poisonous substances, animal nature disgust, elicited by poor hygiene and body functions, and socio-moral disgust, elicited by violations of moral rules. Socio-moral disgust is argued to be an evolutionary extension of primary disgust, but remains closely connected to feelings of physical disgust.
Physical disgust (e.g., from a bad taste or smell) also elicits harsher judgments of moral transgressions (Eskine, Kacinik, & Prinz, 2011; Horberg, Oveis, Keltner, & Cohen, 2009; Schnall, Haidt, Clore, & Jordan, 2008). On the other hand, feelings of physical purity seem to embody personal morality and integrity (Lee & Schwarz, 2010; Liljenquist, Zhong, & Galinsky, 2010). For instance, the mere act of washing one's hands after committing an immoral action appears to alleviate guilt and other negative feelings (Zhong & Liljenquist, 2006), literally washing away one's sins. Feelings of disgust and purity are experienced as more than a physical state of relative cleanliness, but also embody feelings of relative morality.
However, ritual washing is also often used to bestow symbolic purity, (e.g., baptism, mikvah, ablution), and commonly practiced in preparation for contact with sacred objects or activities (e.g., before prayer or entering a temple).
Religion and spirituality are therefore closely bound up in concerns for purity. Religious doctrines not only prescribe cleaning behaviors
that foster physical hygiene, but the act of religious devotion is itself represented as a motivation for spiritual purity. This connection
between religion and purity is so deep-seated it frequently has been taken for granted. Religious purity rituals are often cited to support the case for the embodiment of morality (Graham & Haidt, 2010; Looy, 2004; Zhong & Liljenquist, 2006), and socio-moral disgust has been characterized as a response to violations of “divinity” (Rozin, Lowery, Imada, & Haidt, 1999). Some correlational evidence shows that religiosity is associated with greater obsessiveness (Lewis, 1998), and distaste for “sick” humor (Saroglou & Anciaux, 2004), and other research has shown that exposure to rejected religious beliefs can elicit disgust (Ritter & Preston, 2011). But to date, no empirical work has directly investigated the conceptual or motivational association between religion and cleanliness. The present research aimed to do just that, in three studies.
(You can read the studies at the link)
Results and discussion (of the third study)
Along with Studies 1 and 2, this finding suggests a mutual association between cleanliness and religion, as cleanliness primes increased self-reported value of religion. Although we did not include a control condition here, these findings are consistent with evidence that embodiment of personal cleanliness enhances feelings of personal righteousness (Zhong et al., 2010), and likewise we should expect that clean primes are responsible for these effects. When in a state of physical cleanliness, one adopts an overall sense of personal purity that can be translated into other judgments of the self as “pure” (e.g., morally,
spiritually). Interestingly, these results may seem to be at odds with the “Macbeth effect” (Zhong & Liljenquist, 2006), where recalling past unethical actions motivates physical cleanliness, as a way of compensating for moral impurity. Unlike the Macbeth effect, the “dirtiness” prime did not elicit greater religious value to compensate for feelings of physical impurity. Perhaps the difference arises from the particular threat to self-esteem presented by feeling immoral, that elicits the compensatory goals for physical cleanliness observed in the Macbeth effect. In contrast, feeling physically unclean does not present the same threat
that feeling immoral does, and so does not elicit the same need to compensate. Rather, feelings of physical purity directly embody feelings of spiritual purity. This is consistent with recent evidence that physical cleanliness embodies a sense of moral purity (e.g., Liljenquist et al., 2010). For instance, the same clean prime manipulation we use here has been demonstrated to increase feelings of moral superiority over others (Zhong et al., 2010), suggesting an association between feeling clean and feeling virtuous.
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But one of the possible answers, i.e. "enduring pain from ice water" got me thinking. I've never experienced pain from ice water, so I don't know. Reading about those heart-wrenching frostbite experiments that Nazis and Japanese did before and during the war as a part of their bioweapons research, was so painful it actually took my breath away, literally, for a while... So, I probably wouldn't voluntarily choose that. But jumping into ice cold water after a hot sauna is really enjoyable experience, osit. I don't feel pain. It's a mild shock, but if you moving in the water, it's actually very invigorating and pleasant. I just recently started visiting Korean sauna (highly recommended!) where they have an ice water pool and a so-called "ice sauna" (salt sauna, clay sauna and much more). My daughter and her friend loved it too! As I observed, they can stay in the cold water so much longer than most adults. Sorry, probably, 
