Nicene and Post-Nicene Fathers: Series I/Volume V/On the Spirit and the Letter/Chapter 28

Chapter 28 [XVI]—Why the Holy Ghost is Called the Finger of God.

“Now the Lord is that Spirit: and where the Spirit of the Lord is, there is liberty.” Now this Spirit of God, by whose gift we are justified, whence it comes to pass that we delight not to sin,—in which is liberty; even as, when we are without this Spirit, we delight to sin,—in which is slavery, from the works of which we must abstain;—this Holy Spirit, through whom love is shed abroad in our hearts, which is the fulfilment of the law, is designated in the gospel as “the finger of God.” Is it not because those very tables of the law were written by the finger of God, that the Spirit of God by whom we are sanctified is also  the finger of God, in order that, living by faith, we may do good works through love? Who is not touched by this congruity, and at the same time diversity? For as fifty days are reckoned from the celebration of the Passover (which was ordered by Moses to be offered by slaying the typical lamb, to signify, indeed, the future death of the Lord) to the day when Moses received the law written on the tables of stone by the finger of God, so, in like manner, from the death and resurrection of Him who was led as a lamb to the slaughter, there were fifty complete days up to the time when the finger of God—that is, the Holy Spirit—gathered together in one perfect company those who believed.