"No one can say 'Jesus is Lord' except by the Holy Spirit." "God has sent the Spirit of his Son into our hearts, crying, 'Abba! Father!"' This knowledge of faith is possible only in the Holy Spirit: to be in touch with Christ, we must first have been touched by the Holy Spirit. He comes to meet us and kindles faith in us. By virtue of our Baptism, the first sacrament of the faith, the Holy Spirit in the Church communicates to us, intimately and personally, the life that originates in the Father and is offered to us in the Son.
Baptism gives us the grace of new birth in God the Father, through his Son, in the Holy Spirit. For those who bear God's Spirit are led to the Word, that is, to the Son, and the Son presents them to the Father, and the Father confers incorruptibility on them. And it is impossible to see God's Son without the Spirit, and no one can approach the Father without the Son, for the knowledge of the Father is the Son, and the knowledge of God's Son is obtained through the Holy Spirit.
Source: Catechism of the Catholic Church (Vatican.va)