findOrFail();

The documentation explains it.

https://laravel.com/docs/5.8/eloquent

When you use only find method it's return null when no data found. But and when you use findOrFail method it's throw an Exception when no data found.

a) You FIND it

b) You FIND it OR you FAIL (throw an exception)

1- find($id) takes an id and returns a single model. If no matching model exist, it returns null.

2- findOrFail($id) takes an id and returns a single model. If no matching model exist, it throws an error1.

I am so sorry that I am confused here.

But it is right in the docs

Sometimes you may wish to throw an exception if a model is not found. This is particularly useful in routes or controllers. The findOrFail and firstOrFail methods will retrieve the first result of the query; however, if no result is found, a Illuminate\Database\Eloquent\ModelNotFoundException will be thrown:

Again sorry.