(a) It is narrated from Abu Ma'mar Abdullah bin Sakhbarah (may Allah have mercy on him): We asked Khabbab (may Allah be pleased with him): Did the Messenger of Allah (peace and blessings be upon him) recite in the Zuhr and Asr prayers? He said: Yes! We asked: How did you recognise that? He said: By the movement of his (peace and blessings be upon him) blessed beard.
(b) In this there is evidence that moving the tongue during recitation is necessary.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2432