When the Son completed the work with which the Father had entrusted him on earth, the Holy Spirit was sent on the day of Pentecost to sanctify the Church unceasingly, and thus enable believers to have access to the Father through Christ in the one Spirit. He is the Spirit of life, the fountain of water welling up to give eternal life. Through him the Father gives life to men, dead because of sin, until he raises up their mortal bodies in Christ.
The Spirit dwells in the Church and in the hearts of the faithful as in a temple. He prays in them and bears witness in them to their adoption as sons. He leads the Church into all truth and gives it unity in communion and in service. He endows it with different hierarchical and charismatic gifts, directs it by their means, and enriches it with his fruits.
By the power of the Gospel he enables the Church to grow young, perpetually renews it, and leads it to complete union with its Bridegroom. For the Spirit and the Bride say to the Lord Jesus: “Come!”
In this way the Church reveals itself as a people whose unity has its source in the unity of Father, Son and Holy Spirit.
The whole company of the faithful, who have an anointing by the Holy Spirit, cannot err in faith. They manifest this distinctive characteristic of theirs in the supernatural instinct of faith (sensus fidei) of the whole people when, from the bishops to the most ordinary lay person among the faithful, they display a universal agreement on matters of faith and morals. This instinct of faith is awakened and kept in being by the Spirit of truth. Through it the people of God hold indefectibly to the faith once delivered to the saints, penetrate it more deeply by means of right judgment, and apply it more perfectly in their lives. They do all this under the guidance of the sacred teaching office: by faithful obedience to it they receive, not the word of men but in truth the word of God.
Moreover, the Holy Spirit not only sanctifies and guides God’s people by the sacraments and the ministries, and enriches it with virtues, he also distributes special graces among the faithful of every state of life, assigning his gifts to each as he chooses. By means of these special gifts he equips them and makes them eager for various activities and responsibilities that benefit the Church in its renewal or its increase, in accordance with the text: To each is given the manifestation of the Spirit for a good purpose. These charisms, the simpler and more widespread as well as the most outstanding, should be accepted with a sense of gratitude and consolation, since in a very special way they answer and serve the needs of the Church.
—From Lumen Gentium, Second Vatican Council