Delegating someone to buy something using a credit card
If your friend's credit card is free of this condition, then there is nothing wrong with you delegating him to buy what you want and sending him the money later on.
But if the card has this condition, then it is not permissible for you to delegate him to buy something for you with this card, because if it is not permissible for a person to do a thing, it is not permissible for him to delegate someone else to do it.
It says in al-Mawsoo’ah al-Fiqhiyyah al-Kuwaitiyyah (25/66): It is not acceptable to delegate to someone else that which it is not acceptable for him to do himself, because the agent is acting on his behalf.
Shaykh Ibn ‘Uthaymeen said: This is a principle; everyone who has the power to dispose of a thing is entitled to delegate it to someone else or be delegated by someone else; and if he does not have the power to dispose of it, he does not have the right to delegate it to someone else or be delegated by someone else. Al-Sharh al-Mumti’ (9/90).
What you have to do is look for another way to buy the items you need, especially as there are now a number of credit cards on which you may put a certain amount of money and then use them within the limits of this amount, without there being any interest or riba.
If this credit card is free of this riba-based condition, there is nothing wrong with you delegating your friend to buy things for you, then you can send the money to him later on. This is not regarded as buying currency for currency, in which a hand-to-hand transfer would be stipulated; rather it is a loan to you from your friend.
And Allaah knows best.