"Give that word to all, which you yourselves have received with joy, since you were children," he said, telling them to "read and meditate assiduously on the Word of God in order to believe what you have read, teaching what you have learned in the faith, living that which you have taught."
He told the priests to nourish the people of God with a doctrine that is "simple," explaining that this is how the Lord himself spoke, and it "arrived to the heart."
"Don't give homilies that are too intellectual, elaborate. Speak simply, speak to the heart. And this preaching will be a nourishment," he said, adding that it will also be a "joy and support" for the faithful.
Christ must be the "scent of your life," the Pope said, stressing that "the word without the example of life isn't useful; it's better to turn around, (because) the double life is an bad sickness in the life of the Church."
Pope Francis told the priests to recognize and be aware of what they are doing, primarily in administering the sacraments.
He also said to "imitate what you celebrate, so that participating in the mystery of the death and resurrection of the Lord, you bring the death of Christ into your limbs and walk with him in the newness of life."
"A priest who has perhaps studied a lot of theology, and has received, 1,2,3,4 degrees, but who hasn't learned to carry the Cross of Christ, isn't useful," he said, adding that "he will be a great academic, a great professor, but not priest."
He placed particular attention on the sacrament of confession, during which a priest forgives sins "in the name of Christ and of the Church."
Stressing the importance of mercy, he told the priests "please, I ask you, in the name of Christ and the Church, to be merciful, always."
"Don't load on the back of the faithful, weight that they can't carry, not even you," he said. "Jesus rebuked these doctors, and he called them hypocrites."
Francis also urged them to spend time with the sick and elderly, explaining that perhaps one of the most "boring" or even "painful" tasks they have is visit the sick.
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While it's okay to have deacons or lay members of their parishes go and give communion to them, Pope Francis told the priest to do it themselves. Otherwise, "you don't let yourselves touch the suffering flesh of Christ in the sick. This sanctifies you. You will draw closer to Christ."
He closed his homily telling them to always have before their eyes "the example of the Good Shepherd, who did not come to be served, but to serve," and to seek salvation for the lost.