The Greek verb askeo (ἀσκέω) means "to exercise, train, practice diligently" — used in classical Greek of artisans working their craft and athletes training their bodies. The word is the source of the English word "asceticism." In the New Testament it appears once, in Acts 24:16.
In Acts 24:16, Paul gives his defense before Felix: "So I strive always (askō) to keep my conscience clear before God and man." This is the only New Testament use of the word, but it is theologically rich. Paul applies the language of athletic discipline to his inner life — specifically to conscience. Keeping a clear conscience requires intentional, ongoing practice, not passive hoping. This aligns with Paul's frequent athletic metaphors (1 Corinthians 9:24–27; Philippians 3:14) and with 1 Timothy 4:7 ("train yourself to be godly") which uses the related noun gumnasia. Spiritual maturity is not automatic; it requires disciplined exercise.