On Sunday Pope Francis ordained ten men to the Catholic priesthood, offering advice on the priestly vocation and exhorting them to imitate Christ in their service.

The pope gave his message to the new priests on the 54^th World Day of Prayer for Vocations, at the Vatican, as Catholic News Agency reports.

He implored the priests 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, one, two, three, four 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 emphasised the vocation as one of imitation, with Christ at the center.

'Aware of having been chosen from among men and formed in their favor to attend to the things of God, exercise in joy and sincere charity the priestly work of Christ,' Francis said.

He encouraged the priests to 'be joyful, never sad. Joyful, with the joy of the service of Christ, even in the midst of suffering, incomprehension, of your own sin.'

'Always have before your eyes the example of the Good Shepherd, who didn't come to be served, but to serve,' he said, asking them to 'please, don't be 'lords,' don't be clerics of state, but shepherds, shepherds of the People of God.'

The ordained priests hailed from across the world, but had trained seminaries in the diocese of Rome. While priests represent those chosen by God for particular service in the church, Francis emphasised that Jesus chose men 'not to make a career, but to do this service'.

He encouraged hard study and meditation on Scripture, but invited priests to preach a 'simple' message that will bring 'joy and support' to their congregations.

'Don't give homilies that are too intellectual, elaborate. Speak simply, speak to the heart. And this preaching will be a nourishment,' he said.

He spoke about the importance of administering sacraments such as the Eucharist, confession, as well as practical pastoral work like visiting the sick and elderly.

He warned his audience to avoid hypocrisy in their authority, and following a theme of his pontificate, implored the practice of mercy.

'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.'

He added: 'please, I ask you, in the name of Christ and the Church, to be merciful, always.'