This hymn is an intense, personal prayer for the working of the Holy Spirit (st. 1), for illumination (st. 2), for more fervent love for Christ (st. 3), for greater holiness in our walk with the Lord (st. 4), and for the fullness of the Spirit (st. 5). The first line was changed from "Spirit of God, descend upon my heart" to "Spirit of God, who dwells within my heart."
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.