Keep carefully and watchfully, O happy sinner, this spirit of yours, this most fitting affection of humility and devotion by which you may always so think of yourself in humility and of the Lord in goodness. There is nothing greater that it among the gifts of the Holy Spirit, nothing more precious in the treasures of God, nothing more holy among all the charisms, nothing more health-giving in all the sacraments. Keep, I say, if you wish yourself to be kept, the humility of the sentiment and word by which you confess to your Father and say, Father, now I am not worthy to be called your son: make me one of your hired servants.
This humility not only justifies sinners but also perfects the just and brings their justice to fullness if they confess themselves humble servants even when they have done all they are bidden. Mercy has welcomed you kindly, revived you with loving-kindness.
Humility is the greatest of virtues, although it does not know itself to be a virtue. It is the root and seed-bed, the tinder and incentive; it is the summit and peak, the custody and discipline of all the virtues. From it they begin, through it they make progress, in it they are perfected, by it they are preserved. It is humility that makes all the virtues what they are, and if any one of them be lacking or less perfect, it is humility that compensates for the loss, since it profits by the other’s absence.
Guerric of Igny, Sermon 21 for the Saturday of the Second Week of Lent, Liturgical Sermons, CF 8, p. 143 f.