Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) states: The Prophet (peace and blessings be upon him) would touch his beard during the prayer, without fidgeting.
Bazzar recorded it; its chain contains Isa bin Abdullah, who is from the descendants of Sayyiduna al-Nu'man bin Bashir (may Allah be pleased with him), and he is da'if (weak).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الصلاة / 2463