I read the 'book of characteristics of As-Salat' in Sahih Bukhari. It is mentioned in (1:804) that Dhikr should be 33 times for each mentioned Zikr. While we do 33, 33, & 34, times to complete the number 100. Is there any other Hadith which verifies this practice?
Praise be to Allah, the Lord of the Worlds; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.
Saheeh al-Bukhari is accepted by the whole Muslim Ummah. What is narrated in this book with a full chain does not need to be supported with any other Hadith.
Uttering Takbeer 34 times after the obligatory prayers is narrated in Saheeh Muslim and other books of Hadith.Ka’b bin Ajrah reported that the Prophet (Sallallahu Alaihi wa Sallam) said: There are certain statements which, if one were to utter or observe them at the end of every obligatory prayer, one would not be dismayed. (They are) glorifying Allah thirty-three times, praising Allah thirty-three times and extolling His Greatness thirty-four times. [Related by Muslim]
As for making the Zikr by these words (La Ilah Illah Allah Wahdahu La Sharika Lahu Lahul Mulk wa lahul Hamd wa Huwa Ala Kulli shain Qadeer …) (There is no god but Allah, having no partner with Him, to Him belongs sovereignty and to Him to praise due, and He is Potent over everything) is recommended and it is an independent Zikr which does not have any connection with the Tasbeeh (glorifying Allah) that is mentioned above. Some scholars are of the opinion that it is to be pronounced before the mentioned Tasbeeh.
It is also reported that the Zikr “La Ilaha Illa Allahu Wahdahu La Sharikah Lahu …” could be said just after making the usual Tasbeeh thirty three times according to the Hadith that the Prophet (Sallallahu Alaihi wa Sallam) said: if anyone extols Allah after every prayer thirty-three times, and praises Allah thirty-three times, and declares His Greatness thirty-three, times, ninety-nine times in all, and say to complete a hundred: “There is no god but Allah, having no partner with Him, to Him belongs sovereignty and to Him to praise due, and He is Potent over everything," his sins will be forgiven even if these were as abundant as the foam of the sea.(Muslim)
Imam Al-Nawawi is of the opinion that when a person pronounces Takbeer thirty four times even at that time he should utter the above mentioned words of Zikr. Ibn Hajar after referring to the statement of Al-Nawawi said: "Other scholars are of the opinion that he should implement both Ahadith; some times he should end his Zikr by Takbeer (Allah is The Greatest) and sometimes by Tawheed (La Ilah Illah …). In both cases one should not exceed beyond hundred."
Allah knows best.