Sheikh Sayyed Sabiq states in his well-known book Fiqh Us-Sunnah: “It is recommended to recite takbir and du`aa’ with every throw and to hold the pebble between the index finger and the thumb. Ibn Mas`ud and Ibn `Umar at the time of throwing pebbles used to say, “O Allah! Accept this Hajj of ours and pardon our sins.” Ibrahim said, “The Companions of the Prophet loved that while throwing the pebbles of Al-`Aqabah one should supplicate, ‘O Allah, accept this Hajj of ours and forgive our sins.’ When asked if this supplication should be made at the time of throwing other pebbles as well, he replied in the affirmative.”
`Ata’ said, “When you throw the pebbles, you should utter a takbir with each throw. This is reported by Sa`id Ibn Mansur. According to the hadith of Jabir, the Prophet (peace and blessings be upon him) uttered takbir with each pebble that he threw.”
The author of Al-Fath says, “There is consensus that there is no harm if someone fails to utter the takbir.”
Salman ibn Al-Ahwas reported from his mother that she said, “I saw the Prophet (peace and blessings be upon him) riding his mount at Al-`Aqabah holding a pebble between his fingers and throwing it while others were also throwing pebbles with him” (Abu Dawud).”