Pentecost Sunday celebrates and commemorates the gift given to the Church in the Holy Spirit. Saints, theologians and poets have reflected for centuries on the meaning of the third Divine Person of God, trying to glimpse, however partially, the mystery in which we have been caught up.

And to read the mystics of the Church is to realise that the Holy Spirit is a mystery we’re caught up in here and now. Like a person swept up in the love of another, the Church has been swept into the mystery of Divine Love by being given the very Love that is God.

Here are three quotes that offer profound insight into the mystery of the Holy Spirit.

St Bernard of Clairvaux: the Kiss of the Holy Spirit

St Bernard of Clairvaux was a 12th-century Benedictine whose writings, sermons and ministry led to a renewal in monasticism. He is particularly well known for his sermons on the Song of Songs, treating the lover and beloved in those canticles as an image of Christ and the Church. In Sermon 8, he talks about the significance of the Holy Spirit as the kiss of love between the Father and Son, and the source of our spiritual union with God.

If, as is properly understood, the Father is he who kisses, the Son he who is kissed, then it cannot be wrong to see in the kiss the Holy Spirit, for he is the imperturbable peace of the Father and the Son, their unshakable bond, their undivided love, their indivisible unity …

Living in the Spirit of the Son, let such a soul recognize herself as a daughter of the Father, a bride or even a sister of the Son … For if marriage according to the flesh constitutes two in one body, why should not a spiritual union be even more efficacious in joining two in one spirit? And hence anyone who is joined to the Lord is one spirit with him.

St John Paul II

In 1986, Pope John Paul II published the encyclical Dominum et Vivificantem, in which he expounds upon the nature and role of the Holy Spirit in the life of the Church and the world. Importantly, he points out that the gift of the Holy Spirit is a gift that makes the world more human, since it changes us from within, conforming us to the divine love.

Along this path—the path of such an inner maturity, which includes the full discovery of the meaning of humanity—God comes close to man, and permeates more and more completely the whole human world. The Triune God, who ‘exists’ in himself as a transcendent reality of interpersonal gift, giving himself in the Holy Spirit as gift to man, transforms the human world from within, from inside hearts and minds. Along this path the world, made to share in the divine gift, becomes—as the Council teaches—‘ever more human, ever more profoundly human,’ while within the world, through peoples hearts and minds, the Kingdom develops in which God will be definitively ‘all in all’: as gift and love. Gift and love: this is the eternal power of the opening of the Triune God to man and the world, in the Holy Spirit (§59).

The Venerable Fulton Sheen

Fulton Sheen is remembered for many of his books, broadcasts and sermons, but this is arguably one of the more famous talks he gave. Similar to Bernard of Clairvaux, Sheen talks about the Holy Spirit as the bond of love between the Father and the Son, a bond so real it is a Divine Person.

Love has two terms: He who loves and he who is loved. In love the two are reciprocal. I love and I am loved. Between me and the one I love there is a bond. It is not my love, it is not his love, it is our love—the mysterious resultant of two affections, a bond, which enchains and an embrace wherein two hearts leap with but a single joy. The Father loves the Son, the Image of His Perfection, and the Son loves the Father. Love is not only in the Father. Love is not only in the Son. There is something between them, as it were. The Father loves the Son, whom He engenders. The Son loves the Father, who engendered Him.

They contemplate each other, love each other, unite in a love so powerful, so strong, and so perfect, that it forms between them a living bond. They give themselves in a love so infinite that, like the truth, which expresses itself only in the giving of a whole personality, their love can express itself in nothing less than a Person, who is Love.