What follows is my provisional translation (in other words, not official or authorized; see here for more) of a prayer of Baháʼuʼlláh, the original text of which is published in Ad‘íyiy-i-Mubárakih, vol. 1, p. 143 (selection no. 82).
In the Name of God, the Healer, the Sufficer, the Manifest
Glorified art Thou, O Lord, Thou Who art my God and my Beloved! I beseech Thee by Thy Name, through which Thy mercy hath preceded all things and the Sun of the beauty of Thy hidden title shone forth above the horizon of creation, and through which Thy bounty was perfected unto all who dwell in heaven and on earth, to send down upon this sick one, from the clouds of Thy mercy, that which shall cleanse him of every malady, illness, and affliction. Immerse him, then, in the ocean of Thy healing, O Thou in Whose hands are the Kingdom of decree and the Dominion of ordainment! Thou, verily, doest what Thou choosest; Thou art the Ever-Forgiving, the Most Merciful.
A typescript of the original Arabic text of this prayer appears below (vocalization not mine).