صحيح ابن خزيمه
Sahih Ibn Khuzaymah
جماع أبواب الأذان والإقامةChapters on Adhan and Iqamah
(43) بَابُ الِانْحِرَافِ فِي الْأَذَانِ عِنْدَ قَوْلِ الْمُؤَذِّنِ حَيَّ عَلَى الصَّلَاةِ، حَيَّ عَلَى الْفَلَاحِChapter 43: Turning during the adhan when saying "Hayya ‘ala as-salah, hayya ‘ala al-falah"
Hadith Q387
وَالدَّلِيلِ عَلَى أَنَّهُ إِنَّمَا يَنْحَرِفُ بِفِيهِ لَا بِبَدَنِهِ كُلِّهِ وَإِنَّمَا يُمْكِنُ الِانْحِرَافُ بِالْفَمِ بِانْحِرَافِ الْوَجْهِ
And the explanation of the evidence that the muezzin will turn only with his mouth, not with his whole body, and turning with the mouth is possible by turning the face.
