From The Spiritual Canticles by Saint John of the Cross, presbyter

The inhaling of the air

This inhaling or breathing of the air is an ability of the Holy Spirit, which here asks the soul to love God perfectly. It is called inhaling of the air because it is a most delicate touch and sentiment of love that naturally causes in the soul the desire (aspiration) to communicate with the Holy Spirit. The Holy Spirit in turn, in a manner analogous to breathing, with its Divine Breath, elevates the soul most highly and informs (enlightens) her, since the soul breathes in God the same breath of love that the Father breathes in the Son and the Son in the Father, which is the Holy Spirit itself. All three inhale, breathe, aspire to elevate the soul into her divine transformation. This is because there would be no true transformation if the soul did not unite and transform in the Holy Spirit as with the other two Divine Persons, although in this life this does not take place in such a high glory and a deep and elevated delight, due to the manifest lowliness and overall condition of this terrestrial existence. And, this transformation is such a high glory and such a profound and elevated delight, that there is no mortal tongue fit to describe it, nor can human understanding comprehend it, to the extent that a small part of it can be grasped at all.

In the transformation that the soul possesses in this life, the same aspiration passes from God to the soul and from the soul to God with notable frequency and blissful love, although not in the open and manifest degree proper to the next life. This is what I understand Saint Paul meant to express (Gal. 4, 6) when he said: insofar as you are children of God, God has sent into your hearts the Spirit of His Son, clamoring in prayer to Abba, the Father. This is true of the Blessed in the next life and of the perfected ones in this life, in accordance to the ways described.

One need not marvel at how the soul can achieve such a lofty and sublime state, given that God grants her the mercy to be deified and united in the Most Holy Trinity; God becomes an active participant. How incredible it is that in such a soul His work of understanding, knowledge and love is operating, in the Trinity which is united with her, just as with the Persons of the Trinity. God is participating and working within that same soul.

No knowledge or power can describe how this happens, unless by explaining how the Son of God attained and merited such a high state for us, the power to be children of God, as as Saint John (Jn. 1: 12) says: Father, I want that where I am, those You have given me may also be with Me, that they may see the glory and clarity You have given Me; (Jn. 17: 24) that is, that they perform by participation with us (the Trinity) the same work that I (the Son) do by my own nature, which is to aspire, to breathe the Holy Spirit. Moreover, John adds more: (Jn. 17: 20-23) Father, I do not just plead for these that are present; I also plead for those that are to believe by Your doctrine in Me, that they may all be one substance - in the same manner that You, Father, are in Me and I am in You. May they be in us and us in them as one substance. And the glory and clarity that you have given Me, I have given them, so that they be as one substance, just as We are one; I am in them and You in Me, because they are perfect in that union, as One; so that the world may know that You have sent me, and You loved me. Thus, as You have loved Me, by communicating that same love that You communicated to Me - although naturally not the same, You have loved them by the workings of unity and by the transforming power of love.

It is also understood here that the Son is not asking the Father that the saints be in essence and nature as the Father and Son are, but that rather they be in union by reason of love, just as the Father and the Son are united in love.

Accordingly, souls possess the same goods by participation that the Son possesses by nature. As a result, they are truly divine by participation, and are equals and companions of God. From this Saint Peter (2 Pt. 1: 2-4) said: May grace and peace be fulfilled and perfected in you in the knowledge of God and of Christ Jesus our Lord, in the manner that these things are given to us by all the attributes of His Divine Virtue for life and piety, by the knowledge of the One who called us with His own proper glory and virtue, through which great and promises He deigned; all this so that by these things we are made companions of the Divine Nature. This nature is to make the soul a participant in God operating in Him, the Son, and accompanied by Him: the work of the Most Holy Trinity, in the manner we have already described, by cause of the substantial union between the soul and God. This union, perfectly fulfilled in the next life, in this life can nevertheless attain a great foretaste when one reaches perfection, in the way we have described, although as we have said, it is indescribable.

O souls created and raised for these grandeurs and called to them! What are you doing? In what are you entertaining yourselves? Your pretentions are base acts, and your possessions, miseries. O miserable blindness of the eyes of your souls, since with so much light you are blind and for such great voices you are deaf; not seeing that insofar as you seek greatness and glory, you become miserable and lowly, deprived of so many true goods, made ignorant and indignant! Follow the second thing that the soul asks for, which is:

The song of the sweet nightingale

What is born in the soul from that inhaling of the air is the song of the sweet nightingale. As the song of the nightingale is heard in the spring, when the cold and rain of the winter have passed, the song of the nightingale is melody to the ear and recreation for the spirit; in this same way the actual communication and transformation of love, the Wife, now protected and free of all imperfections, pains and natural darkness, feels a new spring in her spirit, within which she feels the sweet voice of the Husband, which is her sweet nightingale, refreshing and renewing the very substance of her soul, saying (Cant. 2: 10-12): behold my beloved speaks to me: arise, make haste, my love, my beautiful one, and come. For winter is now past, the rain is over and gone. The flowers have appeared in our land, the time of pruning is come: the voice of the turtledove is heard in our land.