If the dynamic SQL statement does not contain any parameter markers, you can use EXECUTE IMMEDIATE instead of PREPARE followed by EXECUTE, for example:
move "DELETE FROM emp " & "WHERE last_name = 'Smith'" to stmtbuf EXEC SQL EXECUTE IMMEDIATE :stmtbuf END-EXEC
When using EXECUTE IMMEDIATE, the statement is re-parsed each time it is executed. If a statement is likely to be used many times it is better to PREPARE the statement and then EXECUTE it when required.