ואל תביאנו לא לידי חטא ולא לידי עברה ועון
which when translated means
"Do not let us come into the grasp of sin, nor into the grasp of transgression and iniquity"
What is the difference between sin (חטא), transgression (עברה) and iniquity (עון)? Sin is an error done by mistake. Transgression is a repeated error that is done out of habit and becomes "normal" to the transgressor. Rav Huna said, "When a person commits a sin and repeats it, it becomes, for him, "permissible" (Yoma 86b). Eventually, even a transgression can escalate to an iniquity, something done intentionally with knowledge and will.
Sin leads to transgression, which leads to iniquity. We are to be careful with sins and nip them at the bud, before they grow.
Source: Rav Schwab on Prayer
