On the cross, Christ said, “It is finished.”
He was not speaking of His sacrifice.
He was speaking of His Passover meal, because He spoke it immediately after receiving the wine/gall on the reed.
All Passover meals Christ or any Jew ever attended had four cups of wine - yet Christ left abruptly after the third cup and immediately went to the Garden of Gethsemane to begin His Passion.
He did not drink the Fourth Cup until He drank the wine on the Cross.
He did not die immediately after saying it is finished because it was His Passover meal that was finished, which ended His Old Covenant and began His New Covenant.
Incidentally His Sacrifice began with the institution of the Eucharist on the night before and wasn’t fully completed until His Resurrection.
For the Greater Glory of God
Now I've heard it all.
Take care.
Hoss