‘Ik onkar’ or ‘Ek Onkar’ is a very sacred mantra for Sikhs all over the world. It is a basic mantra or a devotional hymn offered to their Lord. Also known as the 'mool' mantra , it is said to be Guru Nanak's first teaching sermon.
The literal translation of "ik onkar satnam karta poorak nirabhu niravair akal murat ajuni saibham gur prasad jap Aadh Sach jugaad sach hai bhee sach nanak hose bhee sach " is that there is only one god, whose name is 'Truth'. He is the creator and is without fear. He is without hate and beyond time. He is beyond birth and death. He is self-existent. Meditate in his name, for he was when time began, he has been true for ages. He is true and will be true forever for ages.
This mantra brings so much peace to one's mind and heart that one should listen to it with closed eyes in a meditative mood to bring in blissful gratitude towards the lord. God is one, so one can pay homage to one's own lord by even listening to this 'mool mantra' irrespective of the religion one belongs to.