Interesting question. Clearly the most direct reference made to religion is in the Prioress's Tale, where the stereotypical views of the Catholic church and Jews are represented through the tale of the young boy whose incredible piety and devotion ensure that he gains a place in heaven in spite of the evil of the Jews, who are responsible for his death. This is the most standard, if you like, of the three tales in terms of their spiritual references, as we would expect from the Prioress. Morality and spirituality are shown to be things that are to be eagerly desired and fought for, even though it may bring you hardship in this life to come.
There is therefore a massive contrast between the presentation of such ideas in this tale and in the stories that the Wife of Bath and the Pardoner present. Both clearly show that spirituality and morality for them are personal, incredibly flexible codes that change according to their circumstances and needs. For the wife, morality and spirituality are based around the message of female domination and mastery that is included in the tale. The young knight, let us remember, is rewarded when he has the good sense to let his wife decide in everything for him, and has a happly life in every sense as a result.
The Pardoner presents us with a darkly ironic tale, where the characters in this world are so corrupt and debased that they end up killing each other in their selfish search for advancement. This is a world where characters are shown to operate completely without any moral basis or spirituality. Selfishness rules, and avarice is shown as a very real power that ruins lives and ends them.
The three tales thus present very different ideas in terms of piety, spirituality and morality, ranging from traditional religious views in the case of the Prioress to the anarchic world that the Pardoner presents us with.