Call to Prayers (Adhaan) -
Ibn `Abbas addressed us on a (rainy and) muddy day and when the Mu'adh-dhin said, "Come for the prayer" Ibn `Abbas ordered him to say, "Pray in your homes." The people began to look at one another with surprise as if they did not like it. Ibn `Abbas said, "It seems that you thought ill of it but no doubt it was done by one who was better than I (i.e. the Prophet). It (the prayer) is a strict order and I disliked to bring you out." Ibn `Abbas narrated the same as above but he said, "I did not like you to make you sinful (in refraining from coming to the mosque) and to come (to the mosque) covered with mud up to the knees."
AI Summary
The key points are:
1. The people discussed using a fire, bell, or trumpet to signal the start of prayers, like the Jews and Christians.
2. Bilal was ordered to call the Adhan (call to prayer) by saying the wordings twice, and the Iqama (the call when people are ready to pray) by saying the wordings once.
3. Originally, the Muslims in Medina would guess the time for prayers, until Umar suggested a man should call the people to prayer, and the Prophet then ordered Bilal to call the Adhan.