There can be no doubt about the river referred to, for the prophet says: There is a river whose streams gladden the city of God.
And in the gospel, the Lord himself says: Streams of living water welling up to eternal life will flow from the heart of anyone who drinks the water I shall give him.
He was speaking of the Holy Spirit, whom those who believed in him were to receive.
The river of God is brimming with water; that is to say, we are inundated by the gifts of the Holy Spirit.
And from that fountain of life the river of God pours into us in full flood.
We also have food prepared for us. And who is this food?
It is he in whom we are prepared for life with God, for by receiving his holy body we receive a place in the communion of his holy body.
This is what is meant by the words of the psalm:
You have provided their food, for this is your way of preparing them.
For as well as refreshing us now, that food also prepares us for the life to come.
We who have been reborn through the sacrament of baptism experience intense joy when we feel within us the first stirrings of the Holy Spirit.
We begin to have an insight into the mysteries of faith, we are able to prophesy and to speak with wisdom.
We become steadfast in hope and receive the gift of healing.
Demons are made subject to our authority.
These gifts enter us like a gentle rain, and once having done so, little by little, they bring forth fruit in abundance.
Hilary of Poitiers (c.300-368): @ Crossroads Initiative.