Ruling on delaying the Athaan (call to prayer)
14-1-2014 | IslamWeb
Question:
Is it permissible to delay calling the Athaan (call to prayer) for the reason of an ongoing religious lesson until the lesson is complete, at which time the Athaan would be called and then the Iqaamah (call to establish the prayer) is made directly after that, i.e., directly after the Athaan?
Answer:
All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.
It is most appropriate to call the Athaan at the beginning of its time, due to the persistence on doing so of Bilaal 
the Mu’aththin of the Messenger of Allaah, sallallaahu ‘alayhi wa sallam. However, it is permissible, if the need presents itself, to delay it to any time before the next prayer's time comes, as long as doing so does not cause confusion for the one who hears the Athaan.
The Shaafi‘i scholar Zakariyya Al-Ansaari said: "The Athaan is called when the time arrives, and it is legislated as such until the time departs."
The Hanbali scholar Ar-Ruhaybaani said: "The Athaan is performed at the beginning of the time so that someone who is rushed can pray. On the surface of the issue, though, it is permissible to be called as long as the time for prayer remains."
In brief, the most appropriate view is to advance the Athaan as soon as possible and to interrupt the lesson for that reason.