Adding or removing from related supplications

Q 1: What is the ruling on the increment or decrement that may occur while saying certain authentic Du`a' (supplication)? Does this cancel the reward of this Du`a'? For example, Tasbih (saying: "Subhan Allah [Glory be to Allah]"), Tahmid (saying: "Al-hamdu lillah [All praise is due to Allah]"), and Takbir (saying: "Allahu Akbar [Allah is the Greatest]") should be uttered thirty three times, then concluded by saying La ilaha illa Allah (there is no god but Allah) in the hundred time. So, what happens if those supplications are uttered more or less than hundred times? Moreover, some of the supplications have been included in the Hadith of the Messenger of Allah (peace be upon him), so what is the ruling on saying such Du`a's more or less than the specified times?

A: The choice of Du`a' (supplications) is flexible; a person may choose whatever he needs to supplicate to Allah with, avoiding words that may incur sin. As for the reported Du`a', the manner of saying them is based on Tawqif (bound by a religious text and not amenable to personal opinion) (Part No. 24; Page No. 204) with regard to wording and quantity. Accordingly, a Muslim should be committed to both aspects, with neither increase nor decrease in quantity or wording. There should be no attempt to introduce a change to the already established norms.May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.