The Imitation of Christ, by Thomas a Kempis, tr. by William Benham , at sacred-texts.com
I am the Lover of purity, and Giver of sanctity. I seek a pure heart, and there is the place of My rest. Prepare for Me the larger upper room furnished, and I will keep the Passover at thy house with my disciples.(1) If thou wilt that I come unto thee and abide with thee, purge out the old leaven,(2) and cleanse the habitation of thy heart. Shut out the whole world, and all the throng of sins; sit as a sparrow alone upon the house-top,(3) and think upon thy transgressions with bitterness of thy soul. For everyone that loveth prepareth the best and fairest place for his beloved, because hereby the affection of him that entertaineth his beloved is known.
2. Yet know thou that thou canst not make sufficient preparation out of the merit of any action of thine, even though thou shouldest prepare thyself for a whole year, and hadst nothing else in thy mind. But out of My tenderness and grace alone art thou permitted to draw nigh unto My table; as though a beggar were called to a rich man's dinner, and had no other recompense to offer him for the benefits done unto him, but to humble himself and to give him thanks. Do therefore as much as lieth in thee, and do it diligently, not of custom, nor of necessity, but with fear, reverence, and affection, receive the Body of thy beloved Lord God, who vouchsafeth to come unto thee. I am He who hath called thee; I commanded it to be done; I will supply what is lacking to thee; come and receive Me.
3. When I give the grace of devotion, give thanks unto thy God; it is not because thou art worthy, but because I had mercy on thee. If thou hast not devotion, but rather feelest thyself dry, be instant in prayer, cease not to groan and knock; cease not until thou prevail to obtain some crumb or drop of saving grace. Thou hast need of Me, I have no need of thee. Nor dost thou come to sanctify Me, but I come to sanctify thee and make thee better. Thou comest that thou mayest be sanctified by Me, and be united to Me; that thou mayest receive fresh grace, and be kindled anew to amendment of life. See that thou neglect not this grace, but prepare thy heart with all diligence, and receive thy Beloved unto thee.
4. But thou oughtest not only to prepare thyself for devotion before Communion, thou must also keep thyself with all diligence therein after receiving the Sacrament; nor is less watchfulness needed afterwards, than devout preparation beforehand: for good watchfulness afterwards becometh in turn the best preparation for the gaining more grace. For hereby is a man made entirely indisposed to good, if he immediately return from Communion to give himself up to outward consolations. Beware of much speaking; remain in a secret place, and hold communion with thy God; for thou hast Him whom the whole world cannot take away from thee. I am He to whom thou oughtest wholly to give thyself; so that now thou mayest live not wholly in thyself, but in Me, free from all anxiety.
(1) Mark xiv. 14, 15. (2) 1 Corinthians v. 7. (3) Psalm cii. 7.