Sunan Abi Dawud Book 2, Hadith 200
Let the best among you call the adhan for you, and the Qur'an-readers act as your imams.
When the time of prayer comes, call the Adhan, then call the iqamah, then the one who is oldest of you should act as your imam.
The version narrated by Maslamah goes : He said: On that day we were almost equal in knowledge.
The version narrated by Isma’il says: Khalid said: I said to Abu Qilabah: where is the Qur’an(i.e. why did the Prophet(ﷺ) not say: The one who knows the Qur’an most should act as imam)? He replied: Both of them were equal in the knowledge of the Qur’an.
When the Prophet (ﷺ) proceeded for the Battle of Badr, I said to him: Messenger of Allah allow me to accompany you in the battle. I shall act as a nurse for patients. It is possible that Allah might bestow martyrdom upon me. He said: Stay at your home. Allah, the Almighty , will bestow martyrdom upon you.
The narrator said: Hence she was called martyr. She read the Qur'an. She sought permission from the Prophet (ﷺ) to have a mu'adhdhin in her house. He, therefore, permitted her (to do so).
She announced that her slave and slave-girl would be free after her death. One night they went to her and strangled her with a sheet of cloth until she died, and they ran away.
Next day Umar announced among the people, "Anyone who has knowledge about them, or has seen them, should bring them (to him)."
Umar (after their arrest) ordered (to crucify them) and they were crucified. This was the first crucifixion at Medina.