Join tables in Laravel Eloquent method

How to write this code in eloquent method ?

$product = DB::table('products')
             ->join('purchase', 'products.id', '=', 'purchase.id')
             ->join('sales', 'purchase.id', '=', 'sales.id')
             ->select('sales.*', 'purchase.*','products.*')
             ->get(); 

via Chebli Mohamed