Reason behind saying: 'Subhana Rabbiya Al-`Adhim' in Ruku` and 'Subhana Rabbiya Al-A`la' in Sujud

A: The reason behind saying in Salah (Prayer), "Subhana Rabbiya Al-‘Adhim" in Ruku‘ and "Subhana Rabbiya Al-A‘la" in Sujud is the Hadith authentically reported from the Prophet (peace be upon him) that he used to say this in his Salah: Hudhayfah (may Allah be pleased with him) narrated that the Prophet (peace be upon him) used to say "Subhana Rabbiya Al-‘Adhim" in his Ruku‘ and "Subhana Rabbiya Al-A‘la" in his Sujud. (Related by Abu Dawud in his Sunan) (See ‘Awn Al-Ma‘bud, vol. 5, p. 142) It is also related by Al-Nasa’y in his Sunan. In addition, Ibn ‘Abbas (may Allah be pleased with him and his father) narrated that the Prophet (peace be upon him) said: “As for Ruku‘ (bowing), extol in it the greatness of the Lord, as for Sujud, strive in making Du`a' for you will be more deserving of being responded to. (Related by Muslim in his Sahih [authentic Book of Hadith, vol. 4, p. 196]) Imam Ahmad related another Hadith with the same meaning in his Musnad, vol. 1, p. 155-219. Moreover, `Uqbah ibn `Amir (may Allah be pleased with him) narrated: When the following Ayah was revealed: Then glorify with praises the Name of your Lord, the Most Great. The Prophet (peace be upon him) said: “Make it in your Ruku‘”. And when the following Ayah was revealed: Glorify the Name of your Lord, the Most High, the Prophet (peace be upon him) said: “Make it in your Sujud.” (Related by Abu Dawud in (Part No. 5; Page No. 361) his Sunan, vol. 5, p. 140) Imam Ahmad related another Hadith with the same meaning in his Musnad. Therefore, it becomes clear that Du‘a’, which is said during Salah is one of the Tawqifiy (bound by a religious text and not amenable to personal opinion) matters which can not be said except based on a proof from the Book of Allah or the Sunnah of the Prophet (peace be upon him). We may realize the whole wisdom behind them or even part of it, and sometimes the wisdom may be unknown to anyone but Allah. When a person kneels down and reverentially submits themselves to Allah in Ruku‘, it is appropriate to glorify, extol, praise, and exalt Allah and feel the greatness of standing before Him by saying: “Subhana Rabbiya Al-‘Adhim,” because He is the Greatest, to Whose Might the necks are humbled down. When a person prostrates, they say, “Subhana Rabbiya Al-A‘la,” which is most appropriate to the situation where a person places the most honorable thing in them, that is their forehead and nose, on the ground in a state of utmost submission, obedience, and humbleness to their Lord, they are the closest they can be to their Lord, and it is most suitable to say in this situation: “Subhana Rabbiya Al-A‘la.”May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.