Why do we say in English:
"I heard him say "xxxxxxxx".

"him" is part of the main sentence: "I heard him ..."
"say" --- I checked on the internet. (I attached a picture.)
In English, usually, when we have 2 verbs,
we use "to" before the second verb (infinitive form);
for example:
I want him to learn Japanese.
first verb = want
second verb = to learn
BUT
there are some irregular verbs where we don't use "to":
hear/heard
make/made
see/saw
feel/felt
let
(bid/dare/need - Old English, not used much now)

For example,
I saw him eat an apple.
I let him sit down.


thanks
:)