by Martin Luther
"...when the fullness of time had come, God sent forth his Son, born of woman, born under the law, to redeem those who were under the law, so that we might receive adoption as sons. And because you are sons, God has sent the Spirit of his Son into our hearts, crying, “Abba! Father!” So you are no longer a slave, but a son, and if a son, then an heir through God." - Galatians 4:4-7
The Holy Spirit is sent forth by the word into the hearts of the believers, as here stated, "God sent the Spirit of his Son into your hearts." This sending is accomplished by the preaching of the Gospel through which the Holy Spirit inspires us with fervor and light, with new judgment, new desires, and new motives. This happy innovation is not a derivative of reason or personal development, but solely the gift and operation of the Holy Spirit.
We ought to have no doubt about whether the Holy Spirit dwells in us. We are "the temple of the Holy Spirit."(I Cor. 3:16.) When we have a love for the Word of God, and gladly hear, talk, write, and think of Christ, we are to know that this inclination toward Christ is the gift and work of the Holy Spirit. Where you come across contempt for the Word of God, there is the devil. We meet with such contempt for the Word of God mostly among the common people. They act as though the Word of God does not concern them. Wherever you find a love for the Word, thank God for the Holy Spirit who infuses this love into the hearts of men. We never come by this love naturally, neither can it be enforced by laws. It is the gift of the Holy Spirit.
- Martin Luther
Excerpt from Commentary on the Epistle to the Galatians by Martin Luther (Free Book)