Laravel : Trying to get property 'comments' of non-object

I am new to laravel and eloquent and i have this problem "Trying to get property 'comments' of non-object" and i don't know what is the mistake here

model > Post.php

<?php
namespace App;
use Illuminate\Database\Eloquent\Model;
class Post extends Model
{
    public function comments(){
        return $this->hasMany('App\Comment','id');
    }
    protected $primaryKey = 'post_id';
    //protected $fillable = ['title','body'];
}

model > Comment.php

<?php

namespace App;

use Illuminate\Database\Eloquent\Model;

class Comment extends Model
{
    public function posts(){
        return $this->belongsTo('App\Post','post_id');
    }
    protected $primaryKey = 'id';

}

controller > CommentsController

<?php

namespace App\Http\Controllers;

use App\Post;
use Illuminate\Http\Request;

class CommentsController extends Controller
{
    public function show(){
        $comments = Post::find(1)->comments;
        return view('comments', compact('comments'));
    }
}

view > comments.blade.php

@extends('fixed')
    @section('content')


            <div class="container">
                <div class="col-10">
                    <table class="table table-bordered">
                        @foreach($comments as $comment)
                            <tr>
                                <td></td>
                                <td> </td>
                                <td></td>
                            </tr>

                        @endforeach
                    </table>
                </div>
            </div>

@endsection

and i get that error Error

via Chebli Mohamed