rigorist
Someone who takes the strictest interpretation of a law, religious injunction etc.
These rigorists wanted to borrow Old Testament exclusions from participation in the Temple liturgy and apply them to pregnant women and the sexual relations of married couples.
Where it comes from
From rigour, or its source, Latin rigor, + -ist.
Adapted from the Wiktionary entry rigorist (CC BY-SA 4.0).