There exists quite a fantastic assertion amongst some that claim a Qur’an-centric approach that the ritual prayer was never prescribed by the Qur’an in any form whatsoever nor did the Prophet ever teach such a prayer.
Some others ascribe the ritual Salaah as prayed today as a later invented practice with Persian Zoroastrian influence which did not take canon until 787 CE. (approximately 150 years after the death of the Prophet).
“The later Persian Imams built upon this tale and formulated the current Namaaz. They received strong support from the Persian Zoroastrian mother of (Abbasid) Khalifa Haroon Rasheed, Khaizran (d. 789 CE). Haroon’s Zoroastrian viziers, the Baramika, were only too happy to join hands with the royal mother, Khaizran. So, it was she in concert with others who “canonized” Namaaz according to the desires of the Criminal Imams in (787 CE). Her main philosopher was Imam Al-Khalil bin Ahmad Shikoh, the first ever compiler of Arabic to Persian dictionary, Al-‘Ain” 
The term ‘salaat’ is henceforth variously rendered by them in a manner which completely departs from any reference to ritual prayer and new meanings are pinned to well established Arabic words and phrases of the Qur’an which deal with verses which are traditionally understood as referring to prayer.
AN ASSERTION WITHOUT WARRANT:
Despite there being no Qur’anic support for such baseless claims, there is also absolutely no historical proof that a mass invention of ritual prayer ever took place which introduced this practice into Muslim thought. The latter claim will remain the focus of the remainder of the article.
Such an assertion would require one to accept that Prophet Muhammad (sallallaahu alayhi wasallam) never offered such a ritual prayer as part of God’s ordained religion nor did the earliest Muslims to whom the Prophet preached the Qur’an. Furthermore, for one to accept the stupid assertion, one would need to concede the possibility of a mass conspiracy which introduced this practice en masse from the late 8th century onwards which subsequently erased any record of the invention from all recorded history.
It is well appreciated by academic scholarship, that there exists a dearth of Muslim sources in the first centuries of Islam. To make use of later Muslim sources to challenge the assertion above would easily be dismissible on the grounds that the late Muslim sources only reflected the later change.
However, what is less well known and seldom appreciated is the existence of relevant earlier Non-Muslim sources which exist within decades of the end of the Prophet’s ministry which would strongly refute any assertions of a late invented practice. These Non-Muslim sources are much earlier than the Muslim sources and were not always complimentary to the conquering Arabs who were oft seen by them as aggressors, oppressors, marred with vice and referred to as ‘Saracens’. 
In fact, the criticism against ‘Muhammad’s’ conquerors at times was so intense in some early writings within Non-Muslim sources, that there would be no perceivable reason or interest for them to have attributed any Godly ritual to their aggressors whom they called the ‘Saracens’ (the Arab Muslims).
However, despite such a vitriolic portrayal of the conquering Muslims, an early polemic Christian source in the form of a Coptic homily written within approximately a decade of the Prophet’s death (640’s CE) whilst strongly remaining critical of both the Jews and the ‘Saracens’ (Arab Muslims), confirms that they both fasted and prayed. This is despite the fact that the homily deemed other acts of the Saracens as ‘ungodly’. This source is much earlier than the Muslim sources and the unfounded assertions which place the ‘alleged’ invented practice of prayer as canonised around 787 CE.
The date of the Non-Muslim source (c. 640s CE) is within the time period after the Prophet’s death where arguably many of the Prophet’s closest contemporaries would still have been alive.
“As for us, my loved ones, let us fast and pray without cease, and observe the commandments of the Lord so that the blessing of all our Fathers who have pleased Him may come down upon us. Let us not fast like the God-killing Jews, nor fast like the Saracens who are oppressors, who give themselves up to prostitution, massacre and lead into captivity the sons of men, saying: “We both fast and pray.” 
Given that both fasting and praying was a revered act of worship for the Christians, there would have been no credible interest to invent such a claim on behalf of the ‘Saracens’ if it was not in fact an assertion made by the earliest Muslims and a practice they engaged in.
There is clear evidence in the earliest Non-Muslim sources within approximately a decade of the Prophetic ministry which confirms that the earliest Muslims both prayed and fasted. There would be absolutely no perceivable interest for aggressed Christians to invent such Godly rituals and attribute them to the ‘Saracens’ (Arab Muslims) who they saw as oppressors.
There is absolutely no credible academic warrant or historical proof for the belief that ritual prayer was invented by later generations of Muslims in the late 8th century.
Furthermore, given the strong controversy amongst the earliest Muslims on many political and theological matters which has even given rise to much sectarian bloodshed, the requirement to fast and pray has always remained a bedrock belief amongst all practicing Muslims.
 AHMED, SHABBIR, Islam: The True History and False Beliefs, The Imamist Conspiracy of Namaaz, Page 146
 Whilst mainly carrying a negative nuance, the meaning of the term ‘Saracens’ has changed over a period of time. However, in the context of 7-8th century, it most likely referred to the new Muslims of Arabia. An 8th century polemical work by St. John Damascene, a Syrian monk and priest (born 600’s CE) is known to criticise the ‘Saracens’ as following a Prophet named Muhammad.
“…They are also called Saracens, which is derived from the destitute of Sara, because of what Hagar said to the angel: ‘Sara hath sent me away destitute.’
DAMASCENE. ST. JOHN, Derived from a Translation by Rev. G.N. Warwick of the The Patristic Society, The Fount of Knowledge, An Exact Exposition of the Orthodox Faith, Page 40.
Highlights marked in bold red are my own insertions. They have no bearing on the original text other than they emphasise relevance to the topic at hand. These are merely illustrations and have solely been utilised for educational and explanatory purposes.
 HOYLAND. R. G, Seeing Islam As Others Saw It: A Survey and Evaluation of Christian, Jewish and Zoroastrian Writings on Early Islam (Studies in Late Antiquity and Early Islam), Homily on the Child Saints of Babylon (640’s)