Is it obligatory to comb the beard with one's fingers (takhlil) during ablution (wudu') for Umrah or Hajj, and how is it combed if it is dry?

A pilgrim in the state of ihram is prohibited from removing hair from any part of his body. However, he is permitted to gently rub and run his fingers through his head and beard if he is confident that no hair will fall out. The proof for this is the action of the Prophet, peace and blessings be upon him. If the pilgrim fears that hair from his beard might fall out, he should gently run his fingers through it or rub it with a palmful of water to drench it, without combing it with his fingers. If hair falls out unintentionally, there is no sin upon him.