What is the ruling on some worshippers delaying the takbīrat al-ihrām in order to raise their hands and supplicate?

Scholars differed regarding the desirability of supplicating after the Iqamah and before the Takbirat al-Ihram. Imam Ahmad, in one narration, stated that it is not sunnah, and his companions adopted this view. However, it was also reported from him that it is sunnah, as Al-Mardawi narrated that he (Imam Ahmad) used to supplicate between them and raise his hands.

Evidence for the desirability of supplication is what Ibn Hibban, An-Nasa'i, and Al-Hakim narrated from Sa'd ibn Abi Waqqas, that a man supplicated after the Iqamah, and the Prophet, peace and blessings be upon him, approved of it.

Supplicating after the Iqamah and before the Takbirat al-Ihram is sunnah for the individual praying alone and for the Imam. As for the congregant (ma'mum), the sunnah for him is not to occupy himself with supplication, but rather to say the Takbirat al-Ihram after the Imam and join the congregation.