From a letter to Frate Giusto di Giovanni da Volterra:

I long to see you eating and savouring souls. Take your lesson from gentle First Truth who in His restlessly yearning hunger and thirst for our salvation cried out from the wood of the most holy cross, “I thirst”. It is as if He were saying: “I am more longingly thirsty for your salvatin than I can show you through this finite suffering.” Yes, He is tortured with physical thirst, but that suffering is finite. It is the pain of holy desire, shown us in His thirst for the human race, that is infinite. Oh good and gentle Jesus, You let us know You are thirsty and at the same time You ask for a drink.

He gave His blood out of love and it is with this love that He asks us for a drink. I mean that Jesus, who loves, is asking to be loved and served. It is only right that the one who loves ought to be loved. This is how we give our Creator a drink: when we give Him love for love. But we cannot give it to Him through any service we can render Him; no we must give it to Him in the person of our neighbour.

(Taken from Letter 8 in Letters of St Catherine of Siena, Volume II translated by Suzanne Noffke OP,- published by Arizona Center for Medieval and Renaissance Studies,2001)