What is the ruling regarding a husband's refusal to engage in sexual intercourse, contenting himself with masturbating using his wife's hand almost daily, knowing that he suffers from diabetes, and is there a connection between this and his illness?

A husband must engage in sexual intercourse with his wife according to her desire and his ability. The fact that he makes her masturbate with his hand does not absolve him of this duty. If he is ill with diabetes and exhausted from work, this may affect his ability, but someone who is keen on having his wife masturbate him almost daily is likely not incapable of intercourse more than once a month. Therefore, the husband must fear Allah and ensure his wife's chastity, as this is part of the good companionship enjoined in His (Allah's) saying: "And live with them in kindness. For if you dislike them - perhaps you dislike a thing and Allah makes therein much good." The wife is advised to discuss this with her husband in a good manner.