SQL query to select a User's friends via an associated model

My question is: for a given User, what SQL command could be used to select all associated initiators/initiatees for which the associated Relation is confirmed and of a given type?

The Ruby is as follows:

class User < AcitveRecord::Base
  has_many :relations
end

class Relation < ActiveRecord::Base
  belongs_to :initiator, class_name: "User"
  belongs_to :initiatee, class_name: "User"
end

class CreateRelations < ActiveRecord::Migration
  def change
    create_table    :relations do |t|
      t.references  :initiator
      t.references  :initiatee
      t.boolean     :is_confirmed, default: false
      t.integer     :type
    end
  end
end