Religions are methods of practice, as opposed to faith which is broader, harder to define and has to do with one's actual relationship to the deity. As practices, most mainstream religions have many rules, some of which are so important that breaking them amounts to serious sin, or even a break of fellowship. The rules serve the purpose of social bonding and clan loyalty. If you obey, you are 'IN', and the rest of the group 'has your back'. If you don't obey, you are on the fringe at best, and an outcast at worst. As only one example of many the Roman Catholic Church has rules (that have changed over the decades) around preparation for receiving the Holy Eucharist. In the 50's, the fast before Communion was from midnight, regardless of when Communion was received that day. Later the fast became three hours prior to Communion. It was considered a mortal sin to deliberately break this fast. There was a perpetual abstinence from meat on all Fridays, and that rule has been changed to Fridays during the season of Lent. There are rules around attendance at Mass, and failure to comply results in mortal sin. In fact, if a Holy Day of Obligation falls on a Saturday, Mass must be attended on both Saturday and Sunday, or the rules have been broken, resulting in mortal sin. Saturday evening Mass does not cover both obligations, because the Saturday Mass covers the obligation accruing to the holy day, and not to the following Sunday, with its attendant obligation. The more orthodox branches of Judaism are famous for observance of Law and of traditions. The Hebrew Scriptures and other Jewish writings based upon them describe hundreds of rules or laws that are taken very seriously by the devout. There are some religions, particularly in some Asian traditions, that are not as bound by rules as some of the religions in the west. But no religions are free from rules of any kind, or else it is impossible to consider the religion a 'practice'.