Musannaf Ibn Abi Shayba 2:73

Abu Bakr narrated to us, he said: Ibn Mahdi narrated to us, from Hisham, from Qatadah, that he used to see no harm in a man giving the Adhan while he is not in a state of Wudu. But if he intended to perform the Iqamah, he would perform Wudu.