How to use where conditional in with Larave?

I do request using query:

return Baber::where(function ($query) use ($request) {

    // HERE CONDITION WHERE FOR USER TABLE

})->with("user")->orderBy('id', 'desc')->get();

How can I use where() insode query, that it will be comparabled with user table in with("user")?

I mean the followng:

return Baber::where(function ($query) use ($request) {

        $query->where('user.created_at', $request->date);

    })->with("user")->orderBy('id', 'desc')->get();

via Chebli Mohamed