Q:
How is it to kiss thumbs during Khutba upon hearing the name of Rasool
ALLAH peace be upon him and reciting Durood upon hearing the Ayat-e-Durood?
A: During Khutba it is not allowed to perform Namaz or speak.
In Darmukhtar with Shami on page 158 in part two it is mentioned that
*1. When hear the name of Rasool ALLAH peace
be upon him and Ayate-e-Durood neither kiss the
thumb nor recite Darood Shrif because it is Fard to keep tounge silent
(speechless), instead recite Darod Shreef in heart. This order is for
only during Khutba on other ocassions it is Mustahib to kiss thumbs upon
hearing the respectable name of Rasool Allah Sallallahu Alaihe Wasslam.
In Behr-ul-Ra'iq on page 155 in part two it is mentioned that *2. In the
same book on page 156 it is mentioned that *3. In Fataw-e- Amjadia on
page 286 in part one with refrence of Hidaya it is mentioned that *4.
The same is also mentioned in Fatawa-e-Rizvia on page 741 and 759 in part
three. Allah Ta'ala Knows the best.
*1 
*2
*3
*4 