That's but an empty purse that's full of other men's money.

Money in your possession is not necessarily yours to spend. If it belongs to others, it adds nothing to your own resources, however full your purse appears.

The proverb warns against mistaking access to money for ownership of it. An apparent surplus can conceal the fact that you must account for what you hold.

Use it to caution someone who treats borrowed funds, collected payments, or money held on another person’s behalf as though it were their own to spend.