Mercy has welcomed you kindly, revived you with loving-kindness. Fear the judgment, lest the grace given to you in your humility be taken away from you in your pride. You have chosen to be of little account in the house of your Father; you were content to become as one of the hired servants. Remain in that frame of mind, so that even if you are promoted, you may be advanced to greater things still. Claim for yourself the servitude of a hired servant rather than freedom. Cherish your Father with a son’s devotion, aware of what he has deserved from you; but be content with the humble state and work of a hired servant, aware of your own desserts. Never let humility become displeasing to you; through it you began to please and without it you will begin to displease however great the virtues by which you are distinguished, however dutifully you seem to serve your Father.
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, the summit and peak, the custody and discipline of all 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 the virtues what they are, and if any one of them is lacking or less perfect, it is humility that compensates for the loss since it profits by the other’s absence.
From Guerric of Igny’s Sermon for Saturday of the Second Week of Lent (Liturgical Sermons I, CF 8, pp 143 f)