Laravel Eloquent pass variable to with relationship function

Use use in the closure

->with(['assignment' => function ($query) use ($date){

You can try the following:

$user = User::with(array('relationShipMethod' => function($query) use ($request) {
     $query->wherePivot('column', $request->column); 
}))->first();

relationShipMethod = method with you relationship another table for example users has posts maybe relationShipMethod could be posts method