Asim al-Ahwal عاصم الأحول · The Book of Leading the Prayer (Al-Imamah)

"When the Messenger of Allah(ﷺ) passed away, the Ansar said: 'Let there be an Amir from among us and an Amir from among you.' Then 'Umar came to them and said: 'Do you not know that the Messenger of Allah(ﷺ) commanded Abu Bakr to lead the people in prayer? Who mong you could accept to put himself ahead of Abu Bakr?' They said: 'We seek refuge with Allah from putting ourselves ahead of Abu Bakr."'

"When the Iqamah for prayer is said, there is no prayer except the prescribed prayer."