36 Of this peace of Christ, which dwells in our hearts and is, in effect, the love of God, We can repeat what the Apostle has said of the kingdom of God which also rules by love - "the kingdom of Christ is not meat and drink." ( Romans xiv, 17) In other words, the peace of Christ is not nourished on the things of earth, but on those of heaven. Nor could it well be otherwise, since it is Jesus Christ Who has revealed to the world the existence of spiritual values and has obtained for them their due appreciation. He has said, "For what doth it profit a man, if he gain the whole world, and suffer the loss of his own soul?" ( Matt. xvi, 26) He also taught us a divine lesson of courage and constancy when He said, "Fear ye not them that kill the body, and are not able to kill the soul: but rather fear him that can destroy both soul and body in hell." ( Matt. x, 28; Luke xii, 14)
Source: Ubi Arcano Dei Consilio (Vatican.va)