<?php namespace App;

use Illuminate\Database\Eloquent\Model;

class Notification extends Model {

	protected $fillable = [
		'body',
		'type',
		'topic_id',
		'reply_id',
		'user_id',
		'from_user_id',
	];

	public function user()
	{
		return $this->belongsTo('User');
	}

	public function topic()
	{
		return $this->belongsTo('Topic');
	}

	public function fromUser()
	{
		return $this->belongsTo('User', 'from_user_id');
	}

}

<?php namespace App;

use Illuminate\Database\Eloquent\Model;

class Notification extends Model {

	//

}

--- 
+++ 
@@ -4,6 +4,28 @@
 
 class Notification extends Model {
 
-	//
+	protected $fillable = [
+		'body',
+		'type',
+		'topic_id',
+		'reply_id',
+		'user_id',
+		'from_user_id',
+	];
+
+	public function user()
+	{
+		return $this->belongsTo('User');
+	}
+
+	public function topic()
+	{
+		return $this->belongsTo('Topic');
+	}
+
+	public function fromUser()
+	{
+		return $this->belongsTo('User', 'from_user_id');
+	}
 
 }
Set the relationships for the notification model.
