John 14:17 note 1
171 The Spirit promised here was referred to in 7:39. This Spirit is the Spirit of life (Rom. 8:2), and this promise of the Lord's was fulfilled on the day of the Lord's resurrection, when the Spirit as the breath of life was breathed into the disciples (20:22). The Lord's promise here is different from the promise of the Father concerning the Spirit of power in Luke 24:49. That promise was fulfilled fifty days after the Lord's resurrection, on the day of Pentecost, when the Spirit as the mighty wind blew upon the disciples (Acts 2:1-4). In this verse the Spirit of life is called "the Spirit of reality." This Spirit of reality is Christ (v. 6); hence, the Spirit of reality is the Spirit of Christ (Rom. 8:9). This Spirit is also the reality of Christ (1 John 5:6, 20) that Christ may be realized in those who believe into Him, as their life and life supply.