Is it permissible to deliver messages containing words of love between an imprisoned fiancé and his fiancée, and is there sin upon the one who delivers them?

The fiancée is a stranger to the fiancé until the marriage contract is concluded. It is forbidden for him to send her flirtatious or emotional messages, based on the statement of Ibn ‘Uthaymeen: "The fiancée is a stranger to the fiancé; there is no difference between her and a non-fiancée until the marriage contract is concluded."

Accordingly, it is not permissible for the fiancé to speak with or contact the fiancée except to the extent permitted by Sharia, which is the permissible viewing. Anything beyond that, such as lengthy conversations via phone or other means, is forbidden.

It is also impermissible for you to convey flirtatious messages between engaged couples, as this constitutes aiding in sin. Allah has forbidden cooperation in sin and aggression, as He says: "And cooperate in righteousness and piety, but do not cooperate in sin and aggression. And fear Allah; indeed, Allah is severe in penalty."