Halliday & Matthiessen (1999: 114-5):
As was said above, in quoting, where the projected clause retains its mood, the general verb say can be used whatever speech function is being projected. In reporting, on the other hand, the projected clause is no longer specified for mood; its speech function is signalled by the verb in the projecting clause (asked, ordered, etc.). This gives the projected element more of an ideational status (cf. its treatment in traditional grammar as "object" of the projecting verb), and opens up the way to a series of agnate expressions such as (the king ordered) "Execute him!" / that he should be executed / him to be executed/him executed/his execution.