مشکل در رابطه ی many to many

سلام به همگی دوستان.
من داخل فایل web.php یه روت رو به شکل زیر تعریف کردم .

Route::get('/test' , function (){
    $user = auth()->user();
//    return $user;
    $role = $user->roles;
//    return $role;
    $permission = $role->permission;
    return $permission;
});

وقتی user و role رو return می کنم اطلاعتشون به صورت کامل بر میگرده. ولی وقتی permission رو return می کنم. اررور زیر رو نمایش میده.

 Property [permission] does not exist on this collection instance. 

این کد های مربوط به مایگریشنم.

public function up()
    {
        Schema::create('permissions', function (Blueprint $table) {
            $table->id();
            $table->string('name');
            $table->string('title');
            $table->timestamps();
        });
        Schema::create('permission_role', function (Blueprint $table) {
            $table->id();
            $table->foreignId('role_id');
            $table->foreignId('permission_id');
            $table->timestamps();
        });
        Schema::create('roles', function (Blueprint $table) {
            $table->id();
            $table->string('name');
            $table->string('title');
            $table->timestamps();
        });
        Schema::create('role_user', function (Blueprint $table) {
            $table->id();
            $table->foreignId('user_id');
            $table->foreignId('role_id');
            $table->timestamps();
        });
    }

    /**
     * Reverse the migrations.
     *
     * @return void
     */
    public function down()
    {
        Schema::dropIfExists('permissions');
        Schema::dropIfExists('permission_role');
        Schema::dropIfExists('roles');
        Schema::dropIfExists('role_user');
    }

کدهای مربوط به مدل User

class User extends Authenticatable
{
    use Notifiable;

    /**
     * The attributes that are mass assignable.
     *
     * @var array
     */
    protected $fillable = [
        'name', 'email', 'password',
    ];

    /**
     * The attributes that should be hidden for arrays.
     *
     * @var array
     */
    protected $hidden = [
        'password', 'remember_token',
    ];

    /**
     * The attributes that should be cast to native types.
     *
     * @var array
     */
    protected $casts = [
        'email_verified_at' => 'datetime',
    ];

    public function articles()
    {
        return $this->hasMany(Article::class);
    }

    public function courses()
    {
        return $this->hasMany(Course::class);
    }

    public function roles()
    {
        return $this->belongsToMany(Role::class);
    }

کدهای مربوط به مدل Role

class Role extends Model
{
//    protected $guarded = [];

    public function users()
    {
        return $this->belongsToMany(User::class);
    }

    public function permissions()
    {
        return $this->belongsToMany(Permission::class , 'permission_role' , 'permission_id');
    }
}

کدهای مربوط به مدل Permission :

<?php

namespace App;

use Illuminate\Database\Eloquent\Model;

class Permission extends Model
{
    public function roles()
    {
        return $this->belongsToMany(Role::class , 'permission_role' , 'role_id');
    }
}