Is it permissible, from a Sharia perspective, for a man to use surgical procedures or medical and natural methods to increase the size of his penis (i.e., his 'awrah) for the purpose of enjoying intimacy with his wife, and solely for the sake of preserving marital happiness and for this purpose only?

It is permissible to use medical cosmetic procedures to remove disfiguring, painful, or disabling defects, whether through surgery or otherwise. However, if the intention is merely for adornment or to increase pleasure, such as enlarging or reducing organs (breasts, lips, nose, vulva, penis), then it is not permissible. This is because it is an alteration of Allah's creation and an obedience to Satan. The Messenger of Allah, peace and blessings be upon him, cursed those who do so, as stated in the Hadith (definition) of Ibn Mas'ud, may Allah be pleased with him. Enlarging or reducing the penis also adds the corruption of exposing the grave private parts without necessity.