Albert Barnes Commentary Matthew 10:9

"Get you no gold, nor silver, nor brass in your purses;" — Matthew 10:9 (ASV)

Nor brass. This prohibition of gold, silver, and brass, was designed to prevent their preparing money for their journey. Pieces of money of small value were made of brass.

In your purses. Literally, in your girdles. See Barnes on Matthew 5:38-41.

A girdle or sash was an indispensable part of the dress. This girdle was made hollow, and answered the purpose of a purse. It was convenient, easily borne, and safe.