A favorite quotation from then-Cardinal Ratzinger, later Pope Benedict XVI, now the Pontiff Emeritus Benedict XVI:
In the past the Church was always of the opinion that you could not study theology like any other profession, simply as a means of earning money. For then we are treating the word of God like a thing that belongs to us, and this is not the case. Moses had to take off his shoes before the burning bush. We could also say that those who expose themselves to the radioactive beams of the word of God – indeed those who deal with it professionally – must be prepared to live in such a proximity or else be burned. How real this danger is can be seen by the fact that all the major crises of the Church were connected in an essential way to the clergy’s downfall, for whom contact with the holy was no longer the exciting and dangerous mystery of the burning nearness of the Most Holy, but a comfortable way to make their living. The preparation that is required to be able to run the risk of professional nearness to the mystery of God can find its valid expression in the command of Moses to take off his shoes. Since shoes are made of leather, the hide of dead animals, they were regarded as a manifestation of what is dead. We must free ourselves from what is dead so that we can be in the proximity of the One who is life. The dead – these are first of all the excessive amounts of dead things, of possessions with which people surround themselves. They are also those attitudes which oppose the paschal path: only those who lose themselves find themselves. The priesthood requires leaving bourgeois existence behind; it has to incorporate the losing of oneself in a structural way. The Church’s connecting of celibacy and priesthood is the result of such considerations: celibacy is the strongest contradiction to the ordinary fulfillment of life. Whoever accepts the priesthood deep down inside cannot view it as a profession for making a living; rather he must somehow say yes to the renunciation of his life project and let himself be girded and led by another to a place where he really did not want to go. […] And along the entire path there remains the condition of keeping the contact with the Lord alive. For if we turn our eyes from him we will inevitably end up like Peter on his way to Jesus across the water: only the Lord’s gaze can overcome gravity – but it really can. We always remain sinners, but if his gaze holds us the waters of the deep lose their power.
– A New Song for the Lord, pp. 173-174.