The Holy Spirit, being the third Person of the Holy Trinity, does not have a particular form or body. This means that any image we have of the Holy Spirit is mainly there to help illustrate for us the action of the Holy Spirit, and not the vessel in which the Holy Spirit dwells.
For example, while the Holy Spirit is often pictured as a dove, it does not mean that the Holy Spirit is a dove, but rather that for ancient people, doves represented the divine.
In a similar way we can think about the action of the Holy Spirit as "living water," a symbol that is not often connected to the Holy Spirit.
Living water
St. Cyril of Jerusalem refers to this comparison in a catechetical instruction that is featured by the Office of Readings:
The water I shall give him will become in him a fountain of living water, welling up into eternal life. This is a new kind of water, a living, leaping water, welling up for those who are worthy. But why did Christ call the grace of the Spirit, water? Because all things are dependent on water; plants and animals have their origin in water. Water comes down from heaven as rain, and although it is always the same in itself, it produces many different effects, one in the palm tree, another in the vine, and so on throughout the whole of creation. It does not come down, now as one thing, now as another, but while remaining essentially the same, it adapts itself to the needs of every creature that receives it.
This is an important image, as it brings to mind how water is such a necessary part of human life and is something we all need to drink deeply.
The Holy Spirit is that water, which will help us bear much fruit, as St. Cyril continues:
In the same way the Holy Spirit, whose nature is always the same, simple and indivisible, apportions grace to each man as he wills. Like a dry tree which puts forth shoots when watered, the soul bears the fruit of holiness when repentance has made it worthy of receiving the Holy Spirit. Although the Spirit never changes, the effects of his action, by the will of God and in the name of Christ, are both many and marvellous.
While we may think that we can progress in life without the action of the Holy Spirit in our soul, the reality is that we cannot.
We need the Holy Spirit to water within us the seeds of holiness, so that our faith will grow into a massive tree, an "Oak of Righteousness."
Come Holy Spirit, the Living Water.
