The Thorn in the Flesh by George MacDonald

Within my heart a worm had long been hid. I knew it not when I went down and chid Because some servants of my inner house Had not, I found, of late been doing well, But then I spied the horror hideous Dwelling defiant in the inmost cell⁠— No, not the inmost, for there God did dwell! But the small monster, softly burrowing, Near by God’s chamber had made itself a den, And lay in it and grew, the noisome thing! Aghast I prayed⁠—’twas time I did pray then! But as I prayed it seemed the loathsome shape Grew livelier, and did so gnaw and scrape That I grew faint. Whereon to me he said⁠— Some one, that is, who held my swimming head, “Lo, I am with thee: let him do his worst; The creature is, but not his work, accurst; Thou hating him, he is as a thing dead.” Then I lay still, nor thought, only endured. At last I said, “Lo, now I am inured A burgess of Pain’s town!” The pain grew worse. Then I cried out as if my heart would break. But he, whom, in the fretting, sickening ache, I had forgotten, spoke: “The law of the universe Is this,” he said: “Weakness shall be the nurse Of strength. The help I had will serve thee too.” So I took courage and did bear anew. At last, through bones and flesh and shrinking skin, Lo, the thing ate his way, and light came in, And the thing died. I knew then what it meant, And, turning, saw the Lord on whom I leant.