Querying All Records of All Users who have any instance of purchase behavior in their history

I am trying to write a query that shows me all user ids that in any instance of usage have a particular type of "purchase credit" associated with their account. I have one table, "users" that shows user information, ie, user ids, names, birthdate, etc. and then I have another table that shows all users all instances of credit purchases. I want to pull all credit purchases (not just the type I am looking up) from all users who in any instance of purchase have this one kind of credit purchase in their record. Any help would be much appreciated!