28 But, dear Son of Ours and Venerable Brothers, if one of them is called to undertake sacred missions "then neither the poverty of the cleric nor the needs of the diocese may exempt or restrain you from giving consent, since your people, having at hand, so to speak, the aids of salvation, are far less distant from salvation than the pagans. When such an occasion arises, for the love of Christ and of souls, make the sacrifice of the loss of one of the clergy, if indeed it is to be considered a loss. For the one you have lost as a helper and a companion of your labors, the divine Founder of the Church will replace either by inspiring other applicants for the sacred ministry or by a more generous liberality of graces for the diocese."
Source: Saeculo Exeunte Octavo (Vatican.va)