Narrated from him from Hammad from Rib’i from Muhammad ibn Muslim, who said:
I said to Abu Abdillah عليه السلام: "May a man give the adhan while sitting?" Imam عليه السلام said: "Yes, but he should not give the iqamah except while standing."
Ali Akbar al-Ghaffari
Tahdhīb al-Aḥkām fī Sharḥ al-Muqniʿah, vol. 2, p. 60