Allah (G. B. H)says:{0 you who believe! Bow down and prostrate yourselves. } [Al- Hajj: 77] (pa: 139)

And the hadith about the person who prayed improperly and the Prophet's (P. B. U. H) saying:

"Pray as you have seen me pray".

[Al-Bukhari, Vol. 1, The Book of Athan, Chapter 18/605].

And the general consensus of the Muslim nation.