All perfect praise be to Allah, The Lord of The Worlds, and may His Peace and Blessings be upon our Prophet Muhammad and upon all of his family and companions.

Rushing when praying negates Toma`ninah (Remaining quietly in different postures of prayer), which is a pillar of prayer, and humility, which is the reason for accepting one`s prayer. Allah The Almighty Says {What means}: "The believers must (eventually) win through,- Those who humble themselves in their prayers;" {Al-Mu`minun, 1-2}.

Moreover, Abu Huraira said that a man entered the mosque when God’s Messenger was sitting in it and prayed. He then came and said: “Peace be upon you,” and God’s Messenger replied: “And upon you be peace. Go back and pray, for you have not prayed.” He returned and prayed, then came and said: “Peace be upon you,” to which he replied: “And upon you be peace. Go back and pray, for you have not prayed.” On the third or fourth occasion he said:  “Teach me, Messenger of God,” so he said: “When you get up to pray perform the ablution perfectly, then face the qibla and say: “God is most great.” Then recite a convenient portion of the Qur’an; then bow and remain quietly in that attitude; then raise yourself and stand erect; then prostrate yourself and remain quietly in that attitude; then raise yourself and sit quietly; then prostrate yourself and remain quietly in that attitude; then raise yourself and sit quietly.” A version has, “Then raise yourself and stand erect; then do that throughout all your prayer.” (Bukhari and Muslim.)

Al-Shirbini (May Allah have mercy on him) said: "In order for Ruku` (Bowing) to be considered valid, it is conditioned that one remains quietly in that position, as indicated by the above Hadith. Moreover, the least degree of Ruku` is remaining quietly in that position, then raising oneself and standing erect; then prostrating and remaining quietly in that attitude."

Accordingly, if rushing led to abandoning Toma`ninah during Ruku`, Sujud (prostration) or the sitting between the two prostrations and a person didn`t remain quietly in these positions, then his/her prayer is invalid and must be repeated. However, if he/she repeated their prayer and their wudu`(Ablution) was broken, then he/she must stop that prayer, remake wudu`, and pray again.

This is in case a person was certain of not having performed Ruku` quietly due to rushing in prayer. However, if this was a mere doubt. i.e. he/she wasn`t certain of having rushed in prayer and, accordingly, not having offered Tom`aninah properly, then his/her prayer is valid and doesn`t have to repeat it because there is a Fiqh rule that says: "Certainty can`t be overruled by doubt." And Allah The Almighty Knows Best.