There is one striking similarity in the  key mantra from these religions: Hinduism, Sikhism, Islam, Jainism and Buddhism - "Learning."  The other main religions of the world (Christianity and Judaism) don't seem to have one key mantra.  Here are the mantras:

Gayatri Mantra (Hinduism)

S. Radhakrishna has provided one of the better explanations of the Gayatri mantra:
"We meditate on the effulgent glory of the divine Light; may he inspire our understanding."

Mool Mantra (Sikhism)


Namokar Mantra (Jainism)

"Namokar Mantra" (णमोकार मंत्र) is the fundamental prayer in Jainism and can be recited at any time of the day. While praying by reciting this mantra, the devotee bows with respect to Arihantas, Siddhas, spiritual leaders (Acharyas), teachers (Upadyayas) and all the monks. This worship the virtues of all the supreme spiritual people instead of just worshipping one particular person. It is important to note that the Namokar Mantra does not mention the names of even "Tirthankaras" and Siddhas.

By saluting them, Jains believe they receive the inspiration from them for the right path of true happiness and total freedom from the karma of their soul.Jains do not ask for any favours or material benefits from the "Tirthankaras" or from sâdhus and sâdhvis. This mantra simply serves as a gesture of deep respect towards beings they believe are more spiritually advanced and to remind followers of the Jain religion of their ultimate goal of "Nirvana" or "Moksha".


Namokar Mantra by jules75002

Tisarana: Buddhism


I go to the refuge of the (pure) intellect
I go to the refuge of the  (pure) religion
I go to the refuge of the (pure) conglomeration

Kalma (Islam)
That there is no God to be worshipped except Allaah (the one God) and that Muhammad (peace and blessings of God be upon him) is His Messenger.