صحيح ابن خزيمه
Sahih Ibn Khuzaymah
جماع أبواب الأفعال المباحة فى الصلاةChapters on Permissible Acts in Prayer
(338) بَابُ الرُّخْصَةِ فِي الْإِشَارَةِ بِجَوَابِ الْكَلَامِ فِي الصَّلَاةِ338 Chapter: Permission to Gesture in Response to Speech in Prayer.
Hadith Q889
إِذَا كَلَّمَ الْمُصَلِّي وَفِي الْخَبَرِ مَا دَلَّ عَلَى الرُّخْصَةِ فِي إِصْغَاءِ الْمُصَلِّي إِلَى مُكَلِّمِهِ وَاسْتِمَاعِهِ لَكَلَامِهِ فِي الصَّلَاةِ
And in the hadith, there is evidence that a person performing prayer is permitted to listen attentively and carefully to the conversation of someone speaking to him.
