6 Knowing this, that our old man was crucified with Him, that the body of might be made ineffective, that we should no longer serve sin, 7 for the one having died has been justified from sin. Romans 6:6-7 (translated from the NA28 Greek text)
Romans 6:6 clearly shows us that true believers become holy in Christ. However, there is confusion because many do not look correctly at the Greek verb tenses in this passage. If they simply read it in English or some other translation it is easy to not see that all the verb tenses here are past tenses (aorist or perfect).