How save records on tables with Parent->child->child relationship

Let's say I have three tables.

table A
--------------------
id
description

table b
--------------------
id
a_id
description

table c
--------------------
id
b_id
description

Whenever I do

$a->save();
$a->b()->save();
$a->c()->save();

I get the error BadMethodCallException with message 'Call to undefined method Illuminate\Database\Eloquent\Relations\HasManyThrough::save()'

My a model have a hasManyThrough(C, B) relationship;