Galatians 2:20 "I have been crucified with Christ; it is no longer I who live, but Christ lives in me; and the life which I now live in the flesh I live by faith in the Son of God, who loved me and gave Himself for me." (NKJV)
“I have been crucified with” is actually one word in the original text of the New Testament; and it is the verb around which this verse is built. This verb is sustauroo - a verb found five times in the New Testament and which literally means "to crucify alone with." To better understand this verb we must notice its three inspired grammatical parts. When you classify a Greek verb you state the tense, the voice, and the mood. Sustauroo translated “I have been crucified with” is a perfect tense, passive voice, indicative mood verb.
The perfect tense in Greek describes an action which is viewed as having been completed in the past, once and for all, not needing to be repeated. We all know one very famous usage of the perfect tense. Christ's last cry from the cross, TETELESTAI (“It is finished!”) is a good example of the perfect tense used in this sense, namely “It [the atonement] has been accomplished, completely, once and for all time.” So, here in Galatians 2:20 Paul uses the perfect tense to first say, “I have been crucified alone with Christ”.
The passive voice represents the subject as being the recipient of the action. That adds to the meaning as Paul using the passive voice says “someone else crucified me, I didn’t do it myself.”
The indicative mood is a simple statement of fact. If an action really occurs or has occurred or will occur, it will be rendered in the indicative mood. Paul’s use of the indicative mood adds the meaning that “this really happened to me, it is not hypothetical or fanciful thing - it is a fact.”
So, if we use all the truth of the grammar taken together, Paul says, “What I am telling you is a fact (indicative mood). I have actually already been crucified by God with Jesus Christ (perfect tense). God crucified me and I didn’t do it myself; it happened and was completed in the past, once and for all, and never needs repeating(passive voice).”
Taken from "Good Friday" by Discover the Book Ministries (used by permission).