Is it permissible in prayer to repeat verses or some parts of the Tashahhud that the worshiper uttered without concentration?

Repeating a verse in prayer for the purpose of reflection and moving the heart is permissible, except that repeating verses from Al-Fatihah may interrupt the essential continuity of its recitation according to some scholars. As for repeating the Tashahhud or a part of it, there is no basis for it in the Sunnah. If a person is afflicted with whisperings (waswasa), repetition may increase their whisperings and doubts.