Q. 53. What dost thou believe concerning the Holy Ghost?
First, that He is true and co-eternal God with the Father and the Son; secondly, that He is also given me, to make me by a true faith, partaker of Christ and all His benefits, that He may comfort me  and abide with me for ever.
 Genesis 1:2; Isaiah 48:16; 1 Corinthians 3:16;  Matthew 28:19; 2 Corinthians 1:22;  Galatians 3:14; 1 Peter 1:2;  Acts 9:31;  John 14:16; 1 Peter 4:14.
Reformed dogmatics is classically presented under six loci, viz. Theology (doctrine of God and His creation and providence), Anthropology (doctrine of man in relation to God), Christology (doctrine of the person and work of the Lord Jesus Christ), Soteriology (doctrine of the application of the work of redemption), Ecclesiology (doctrine of the Church and of the means of grace), and Eschatology (doctrine of the last things). It is interesting to note the omission of Pneumatology (doctrine of the Holy Spirit) as a major locus. The reason for this omission is that the person of the Holy Spirit is generally dealt with under the first locus as part of the presentation of the doctrine of the Triunity of God. Moreover, the work of the Holy Spirit is generally covered under the fourth locus, as the Holy Spirit is the Third Person of the Godhead, who is especially responsible for the application of the redemption purchased by Christ, to the individual believer. This is how the Westminster Standard deals with Pneumatology. However, it is useful for these points to be gathered and reiterated as it is done here in the Heidelberg Catechism.
Here we are told first of all about the Person of the Holy Spirit. He is same in substance, equal in power and glory with the Father and the Son. Secondly, we are taught that He is sent by the Father and the Son to us, in order to apply the benefits of redemption decreed of the Father and procured by the Son. He does so firstly by working faith in us in our regeneration or effectual calling, thereby enabling us to embrace the Lord Jesus Christ as our Saviour and Master as He is presented to us in the Gospel (Gal 3:14). Secondly, having indwelt us at our new-birth, He continues to sanctify us, causing us to die more and more unto sin and live more and more unto righteousness as we make diligent use of the means of grace (1 Pet 1:2; 2 Thes 2:13; Rom 8:11; Phil 2:13). Thirdly, the Holy Spirit illumines our hearts that we may understand the Scriptures when we read or hear it (1 Cor 2:14), and then He brings to mind all that we have learned or have been taught (Jn 14:26). Fourthly, He assures us of the Father’s love (Rom 8:15; 5:5), and comforts us in times of trials and afflictions (Acts 9:31). Fifthly, the Holy Spirit abides with us and therefore preserves us in our faith for ever (Jn 14:16; 1 Pet 4:14).
The doctrine of the Holy Spirit is a much disputed and misunderstood subject. Throughout the history of the Church there have been sects which refuse to acknowledge the personality and divinity of the Spirit. Today, these are mainly found amongst Liberal Unitarians, Jehovah Witnesses and other cults, all of which, we would not regard as being Christian. Then there are those who see a sharp discontinuity between the Old and New Testaments, who would argue that the Holy Spirit did not indwell believers in the Old Testament, thus effectively teaching that God has two people and two ways of salvation. These are the classical Dispensationalists. Then there are those who argue that the Holy Spirit’s baptism is a second blessing (from regeneration and indwelling), and that those who receive it would break out in tongues and other manifestations. These are the Charismatics and Pentecostals. In this short article, we are unable to address all these errors. But it behoves the believer to look them up and study how we may give an answer to those who teach these false doctrines should we have occasions to be confronted by them.
Heidelberg Catechism >