Ruby on Rails Nested Resources

Good day, I am very new in this of rails and I am following a facilitated code course, I am in the part of nested resources and I get the following error. Can someone give me a hand? From Ya thousand thanks

ActiveModel::MissingAttributeError in Articles#show

Extracted source (around line #1):
<%= form_for(@article, @comment) do |form| %>
  <% if @comment.errors.any? %>
    <div id="error_explanation">
      <h2><%= pluralize(@comment.errors.count, "error") %> prohibited this comment from being saved:</h2>

      <ul>