Unitarianism, Prayers, Almsgiving, Fasting, Pilgrimage and Exerting in the way of righteousness were part of all true forms of religion throughout history.
Consider ‘The Model Prayer’ of the Bible, also known as ‘Lord’s Prayer’, which says, “…Our Father in heaven, Hallowed be Your name, Your kingdom come, Your will be done, On earth as it is in heaven. Give us this day our daily bread, And forgive us our debts, As we forgive our debtors, And do not lead us into temptation, But deliver us from the evil one, For Yours is the kingdom and the power and the glory forever, Amen.” (Mathew 6:9-13)
Then see ‘The Gayatri mantra’ of ‘The Holy Vedas’, which says, “O Supreme Lord! Thou art ever existent, Ever conscious, ever blissful. We meditate on Thy most adorable glory. Mayest Thou guide and inspire our intellect, On the path of highest divinity! May we be able to discriminate, Between truth and falsehood.” (Rig.3.62.10)
Also understand ‘The Opening’ chapter of the Qur’ān recited in every cycle of Salah, saying, “In the name of Allah, the most Gracious, the Most Merciful, All praise is due to Allah, the Lord of the Universe; the Beneficent, the Merciful; Lord of the Day of Judgement. You alone we worship, and to You alone we turn for help. Guide us to the straight path; the path of those You have blessed; not of those who have incurred your wrath, nor of those who have gone astray.” (1:1-7).
In all the above three prayers adored in Christianity, Hinduism and Islam respectively we find striking similarity in content distinctly divided in three parts, namely praising of the Lone Lord, definition of His relation with us and seeking of His true guidance away from falsehood.
‘Yoga’ in Sanskrit has the connotation of ‘communion with Lord’, while the Meraj-un-Nabi has the meaning of ‘communion of Apostle with the Lord’ as also Salah, the Muslim prayer, is considered Meraj of the believer in Islam.
While every book on Yoga insists that it is a form of prayer and particular mantras to be uttered are associated with every aasana or physical posture, we find no consistency in the aasanas and the associated mantras in different books on Yoga. There is no common sequence in different aasanas for different physical health problems.
An honest study perhaps would suggest that Yoga must have been a congressional form of prayer similar to the five times salah of Muslims.
While attending Christian prayers in School Church and in Christian Mission Hospital in my village, I witnessed the attendees falling in prostration (sajdah) in a very similar way we do in masjid.
‘Sashtanga Namaskaram’, for example, designates the touching of eight parts of body on the ground. It is like the touching of nine bones in prostration or Sajdah of the Muslim prayer.
The six pillars of Islam namely Shahadah, Salah, Saum, Zakat, Hajj and Jihad are but the latest in their forms that existed in all religions foregoing in history as mentioned above.