There are various synonyms for the phrase "commit sin". Some of these synonyms include transgress, violate, trespass, err, fall short, and deviate. These words suggest that someone has crossed a moral or ethical boundary by engaging in behavior that is deemed inappropriate or unacceptable by society or religious institutions. Other synonyms for committing sin might include words like offend, do wrong, or go astray. These words all capture the sense of wrongdoing and moral deviation that is associated with the concept of committing sin. Ultimately, the use of any of these synonyms suggests that there is an expectation of moral uprightness that someone has fallen short of.