Musannaf Ibn Abi Shayba 2:147

Ali bin Hashim narrated to us, from Ibn Abi Layla, from al-Hakam, from Ibrahim, who said: If you are in your house or on your journey, the Iqamah is sufficient for you. And if you wish, you may perform the Adhan, except that you should not neglect to repeat the phrases of the Iqamah twice.