Clement of Alexandria — Stromata 2.15

What is voluntary is either by appetite, or by deliberate choice (προαίρεσις), or by thought. Sin, mishap, and injustice sit next to one another in this range: living in luxury and license is a sin; striking a friend as an enemy from ignorance is a mishap; tomb-robbery or temple-robbery is injustice.

Sinning comes from not knowing what must be done, or from being unable to do it. But it is in our power (ἐφ’ ἡμῖν) both to present ourselves for training and to obey the commandments. If we refuse to share in them, we will sin — or rather, wrong our own soul.