The kingdom of heaven is like a treasure which a man found in a field, which he hid, and for which he sold all he had and bought that field.

 Matt 13:44

At that time Jesus spake unto His disciples this parable: “The kingdom of heaven is like unto treasure hid in a field.” And so on.

The treasure is the desire for heaven, the field wherein it is hidden is the earnest observance wherewith this desire is surrounded. Whosoever turneth his back upon the enjoyments of the flesh, and by earnest striving heavenward, putteth all earthly lusts under the feet of discipline, so that he smileth back no more when the flesh smileth at him, and shuddereth no more at anything that can only kill the body; whosoever doth thus, hath sold all that he had, and bought that field.

- Pope St Gregory the Great