What is the ruling on the engaged couple going out to take care of wedding necessities, accompanied by a female mahram?

Islamic law prohibits khalwah (private seclusion) with a non-mahram (definition) woman. A fiancée, before the marriage contract is concluded, is considered non-mahram. Therefore, it is permissible for a man to go out with her if a mahram is present, provided that fitnah (temptation or discord) is avoided and no khalwah occurs. However, after the marriage contract is concluded, she becomes his wife, and it is permissible for them to go out alone, even if the wedding ceremonies have not yet taken place.