Hasan al-Basri (may Allah be pleased with him) states: The Prophet (peace and blessings be upon him) would touch his beard during the prayer.
Abu Ya'la recorded it, and it is mursal (the Companion is missing from the chain).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الصلاة / 2466