Humility is the soil in which the tree of love grows. God the Father to St. Catherine of Siena:

'Wherefore I reply that this is the way, if you will arrive at a perfect knowledge and enjoyment of Me, the Eternal Truth, that you should never go outside the knowledge of yourself, and, by humbling yourself in the valley of humility, you will know Me and yourself, from which knowledge you will draw all that is necessary.'

'After the soul has come to know herself she finds humility and hatred for her selfish sensual passion, recognizing the perverse law that is bound up in her members and is always fighting against the spirit.'

And one more from the Source of Life:

'Charity, it is true, has many offshoots, like a tree with many branches. But what gives life to both the tree and its branches is its root, so long as that root is planted in the soil of humility. For humility is the governess and wet nurse of the charity into which this branch of discernment is engrafted.'