postgres tutorial 13 procedure

CREATE OR REPLACE PROCEDURE transfer(INT, INT, DEC)
LANGUAGE plpgsql   
AS $$
BEGIN
    -- subtracting the amount from the sender's account
    UPDATE accounts
    SET balance = balance - $3
    WHERE id = $1;

    -- adding the amount to the receiver's account
    UPDATE accounts
    SET balance = balance + $3
    WHERE id = $2;

    COMMIT;
END;
$$;

CALL transfer(1,2,1000);