Moreover this is protected water. There is a watchman! Only if he allows you, you can draw water. That watchman is called the Guru!
Among such mantras the mahAvakyas that identify the JivAtmA with the ParamAtmA without any distinction are at the peak. The Acharya speaks of them (in Aitareya Upanishad Bhashya 1.3.13) as sounds that wake you up to Atma-jnAna, the advaita jnAna that lies dormant in the JivAtmA that is sleeping in Ignorance.
It is the Guru that trumpets the drum of the MahAvakyas, wakes you up, as it were, from your sleep, thus waking you up to Enlightenment.