When should a person begin praying (Rak'ah) upon hearing the caller to prayer (Mu'adhin)?
Chapter on Adhan
Al-Mughni
Book of Prayer
Primary text
It is recommended that one's bowing (Rukū') occurs after the Mu'adhin finishes the call, or when he is near finishing. This is because it is stated that Satan flees upon hearing the Adhan, and thus one should not rush to stand up immediately. This view is supported by the practice of Ahmad.
Supporting text
If a person enters the mosque and hears the Mu'adhin, it is recommended that he waits for him to finish and repeats what the Mu'adhin says, thereby combining two virtues. However, if he does not repeat the Adhan and immediately begins his prayer, there is no harm.