What is the text of the legal proxy for marriage?

There is no specific formula required for agency in marriage; rather, it is established by anything that indicates it. So, if you wish to appoint someone to act on your behalf in your marriage contract, you can say or write: "I appoint so-and-so to conclude my marriage contract," or "I make him my representative." And if you wish to appoint someone to arrange the marriage of your daughter or a woman for whom you are the marriage guardian, you can say or write: "I appoint so-and-so to arrange the marriage of so-and-so," or "I make him my representative in this matter." All of this should ideally be documented.