The text begins with a prayer for the working of the Holy Spirit in our hearts (st. 1). It then uses the metaphors of light, fire, and the dove to enable us to see the Spirit's work more clearly: "Come as the light" is a prayer for illumination (st. 2); "Come as the fire" is a prayer for cleansing (st. 3); and "Come as the dove" is a prayer for peace and unity (st. 4).
Bert Polman, Psalter Hymnal Handbook
Since it is uniquely the work and passion of the Holy Spirit, who is “our Sanctifier by living in our hearts” (Belgic Confession, Article 9) and “by the work of the Holy Spirit [God] regenerates us and makes us new creatures, causing us to live new life and freeing us from the slavery of sin” (Belgic Confession, Article 24), we plead for his power to continue this work. The Holy Spirit restores us into God’s image “so that with our whole lives we may show that we are thankful to God for his benefits, so that he may be praised through us...” (Heidelberg Catechism, Lord’s Day 32, Question and Answer 86). We come to know, therefore, that our growth in holy living will not occur without the Holy Spirit’s ministry.