session.BeginTransaction() and transaction.Commit()

I am new to Nhibernate, so my query may seem trivial to you.

We generally embed data operation code inside

  using (var session = sessionFactory.OpenSession())
  {
    using (var transaction = session.BeginTransaction())
    {
       ...Code for CRUD operations
       transaction.Commit();
    }
  }

Because we generally BeginTransaction/Commit/Rollback for saving/updating/deleting data,

I wonder if BeginTransaction() and Commit() are required even if I am retriving data using session.Get<T>(id); or session.CreateCriteria<T>().List();

Please guide.

Thank you!