Trigger novice needs help

I'm trying to create my first database trigger and am having a little trouble. Here's what I want to do. When someone tries to delete a row from table1, I want the row first to be inserted into table2 before it gets deleted. Sounds simple enough. But when my trigger fires I get the following error...

DELETE FROM table1 WHERE provider = '31041'

            *
ERROR at line 1:
ORA-04091: table CHA.TABLE1 is mutating, trigger/function may not see it
ORA-06512: at line 2
ORA-04088: error during execution of trigger 'CHA.TRIGGER1'

Here's what my trigger looks like...

CREATE OR REPLACE TRIGGER trigger1
BEFORE DELETE ON table1
FOR EACH ROW
BEGIN

	INSERT INTO table2
		(SELECT * FROM table1 
		WHERE provider = :old.provider);