Note 11 at Jn. 19:30: When Jesus cried, "It is finished," He was not referring to the whole plan of salvation as being completed. He still had to descend into the lower parts of the earth and lead the captives out (Eph. 4:8-9), as well as come back from the dead and ascend to the Father to make intercession for us (Heb. 7:25). Paul made it very clear in 1 Corinthians 15:14 and 17 that if Jesus wasn't raised from the dead, then our faith is vain and we are yet in our sins.

Therefore, Jesus must have been referring to His ministry here on earth and the Old Covenant law that had now been fulfilled in Christ (Mt. 5:17).