Such an affliction pierces the heart of a parent, and you do well to bring this burden to the Lord of all. Remember the Apostle Paul, who when he yearned for his brethren prayed night and day exceedingly, not only to see their face but to perfect what was lacking in their faith. In the same spirit, let your cries for your son’s lungs and kidneys rise without ceasing, yet seek not merely the mending of flesh but the perfecting of both his soul and yours through this trial.
Our Lord Himself, when He walked among us, often healed on entreaty, yet He required faith as the measure of His mercy. To the blind men He did not say, "Believe ye that I can entreat the Father," but, "Believe ye that I am able to do this?" For He is the Very Son of God, the true Light that dawns upon every man, and all power belongs to Him. Draw near then with boldness and the words of a humble heart: "Speak the word only, and my son shall be healed." Do not consider Him as a mere man, a king of Israel only, but as the Lord of all creation, who out of great lovingkindness delays even judgment that sinners might turn and live.
Yet if the healing tarries, do not lose heart. For as a tree may bear ten strokes and seem unmoved, only to fall by one blow that finishes the work of all, so often souls that hear the word many times without visible fruit later bring forth an abundant harvest. Persist, then, and do not grow weary. The Lord who arranged that Abraham should offer up Isaac before Him, that He might seem to do nothing great in giving His own Son, will not forget your tears. He who did not spare His only Begotten, how shall He not with Him freely give us all things? Even David, when his friend Jonathan was taken, continued to show steadfast love to his children. How much more will your heavenly Father care for your child, in body and in soul?
I join my supplication to yours, praying that the light of the glorious Gospel may dawn upon your son, restoring his strength and filling him with the knowledge of the Son’s love. May he, being raised up, walk as a child of God, hearing and keeping Christ’s commandments, and in so doing love both the Son and the Father. And remember, whether in healing or in prolonged trial, the Lord’s purpose is ever to lead you from earthly entreaties to the confession of Peter: "Thou art the Son of God," and to make you a partaker of everlasting consolation. Cease not, therefore, to knock at the door of His mercy, for the prayer offered in faith shall save the sick, and the Lord shall raise him up.