Calvin: Justified, Believer Becomes One with Christ...

"To sum up the whole, this passage, first, teaches us to behold Christ with the eyes of faith; and, secondly, it informs us, that every one who is regenerated by the Spirit, and gives himself up entirely to God for true justification, is thus admitted to the closest union with Christ, and becomes one with him."

Calvin, John. Complete Commentaries - Matthew 12:48