Does prayer become invalid by adding to it, such as saying: "Our Lord, and to You be all praise and thanks" after rising from bowing, or "My Lord, forgive me and my parents" between the two prostrations, or "I seek help in Allah" when reciting "You alone we worship and You alone we ask for help"? And what is the criterion for extraneous speech that invalidates prayer?

Speaking about matters unrelated to the prayer invalidates it, as the Prophet, peace and blessings be upon him, said: "Indeed, this prayer is not suitable for any of people's speech; it is only for tasbeeh (glorification), takbeer (magnification), and recitation of the Qur'an." As for adhkar (remembrances) and supplications that are not explicitly ورد (reported), they do not invalidate the prayer because they are of the same permissible type of speech within it. Examples include saying "I seek Your help, O Lord" when reciting "You alone we worship, and You alone we ask for help," or adding to the reported dhikr between the two prostrations. However, it is preferable to stick to what is authentically reported.